In the world of competitive pokemon, what people refer to as "basic" represents a much larger portion of the game than the "basic" of the casual player.
For instance, competitive players expect everyone to know their way around stat manipulation, some knowledge of damage calculation and the effect and uses of almost all moves and abilities in addition to what casual players would consider basic. This last stuff includes, but is not limited to:
Typings
Type advantages
Evolutions
The existance and effect of most items
The existance and effect of most tms
Breeding
etc.
In the following article, I will detail what I meant by the aforementioned competitive basics.
Stat Manipulation:
This is pretty much the first step in going competitive. When you start manipulating the stats of your pokemon in order to make them stronger, you know you've stopped playing pokemon as a kiddie game and are looking for a challenge. There are various ways to go about it, and the combination of all of them result in a pokemon ready for the battle arena.
-Base STATS-
The first thing to know about pokemon stats is that inadvertantly, some pokemon are naturally stronger than others. Each pokemon is inherent to a species, and they all have their species specific "base values". They should be considered as your pokemon's dna data. Like in the animal kingdom where an Elephant will always be stronger than a mouse, Gengar will always have more special attack than ryhorn. Base stats usually come in the form of rounded numbers, and are used similar to the way stats growth in other rpgs are. For instance, a pokemon with a base stat of 130 could potentially reach as high as 394 when leveled up to 100 with perfect conditioning, or as low as 238 with perfect neglect. Having general knowledge of where each pokemon stand in the food chain of each stats is important in both countering a pokemon and using a pokemon.
-Natures-
*for more information on natures, find the nature guide on the academy page*
Pokemon natures are, simply put, their personalities. a pokemon's personality will augment a pokemon stat by 10 percent and drop another by 10. In pokemon, it is more advantageous to have specialized pokemon with specific roles rather than have jacks of all trades or all rounders. In that regard, it is recommended to have a nature that augments the most important stat and drop the one your pokemon's specialization has the least use for. For example, there's no point in giving defensive or attack nature to a Butterfree, as even weaker pokemon will still hit you hard. Augmenting butterfree's speed or sp.atk would be the better option. The same is true for EVs.
-IVs-
Individual values are, basically, natural talent your pokemon was born with. There is an ev value for every stat ranging from 0 to 31, and are stats that will be naturally added in your stat total as you level up. Obviously, it is usually better to have stats as high as possible in everything. It is possible to have as low as all 0s and as high as all 31s. Hidden Power's type and power depend on IVs.
-Evs-
*For more information on effort values, find the EVs guide on the academy page*
The effort points you invest in your stats increase them by one for every four points. Or at least, in theory. See, even effort points are affected by Base stats, and naturally, a higher base stat will benefit even more from evs than a lower base stat.
Overview:
Knowing what pokemon are naturally faster/stronger/tougher is important in understanding what to expect from your opponent. You wouldn't expect thunderpunch from an alakazam because alakazam has weak atk. Likewise, you most likely wouldn't use it on your own alakazam for the same reason. If you trained your steelix in defence and your opponent's aerodactyl hurt it, you should assume aerodactyl was trained more in atk than speed. That way, even pokemon with 100 or higher base speed could outspeed it if they maxed their speed stat. This is a lot to take in and is expected to naturally sink in as you progress and play against a lot of different people and teams.
Damage Calcs:
Damage calculation is the world of math geeks. The formula behind it is fairly long and complicated, and nobody expects you to just calculate how hard you hit your opponent on the spot. However, with knowledge of base stats and the process of damage calculation, it is possible to expect damage in a cerrtain range. Here are the most important variables, or "multipliers" you should know about, in no particular order as they are all important; STAB, Weaknesses and resistances, attacker's offensive stat, defender's defensive stat, item boosts, ability boosts, weather boosts, base power.
-Offensive/Defensive stat dynamic-
THE most obvious part of the equation in a stat-indulged game. Pokemon uses a physical/special mechanic that is comparable with strenght and magic in other forms of rpgs. Physical attacks that have a material basis for a hit will use the offensive pokemon's attack stat, and the defending pokemon will resist it with its defense stat. If you use body slam, your muscles will hit my guard. Moves in this category include all slashing moves, punches, falling rocks, earthquakes and tackles. On the other side of the spectrum, you have special moves. They use the offensive pokemon's special atk stat and is matched up with the defensive pokemon's special def stat. Special moves include psychic shock waves, flame breaths, beams and blasts of water. Note that there are various ways to increase or decrease these stats mid-battle. Burns halve your attack stat, and support categorified moves have a myriad of weird effects. They are important, and you MUST use them at your advantage.
-Base Power-
Each and every attacking move in the game are coupled with a power and accuracy stat. The higher the base power, the stronger the move, and the lower the accuracy, the higher the chances that you miss. Note that powerful moves tend to have setbacks, and weaker moves tend to have hax chances. For instance, close combat will reduce your defensive stats after using it, and energy ball has a chance of dropping your opponent's special def stat.
-S.T.A.B.-
Same type attack bonus, abbreviated stab, occurs when a pokemon uses an attacking move of the same type as it. under stab, the base power of a move is multiplied by 1.5. What that means is that a ground pokemon's earthquake is normally stronger than an aerodactyl's. Pokemon with more than one type have STAB on both of their types. This also means that a stab earthquake has higher power than a non stab super effective bubblebeam.
-Weaknesses and resitances-
When a move hits super-effective, the power is multiplied by 2. When it hits super effective on both defending types, (such as a thunderbolt on a gyarados) the damage is multiplied by 4. The reverse is also true, hit not very effective on a pokemon and damage is multiplied by 0.5 (in other words, divided by two) and not very effective on both types, multiplied by 0.25 (divided by 4) This si the reason why you want moves than can hit pokemon that resist your stab as well as moves that can eliminate pokemon that can hit super effectively on you. Also, keep in mind that damage multiplyers stack. In other words, stab is also multiplied when you hit with super effectives.
-Item Boosts-
Many items in the games affect very concretely the damage output of your pokemon. For example, the life orb item hurts you every time you attack. However, the damage output is multiplied by 1.3 (30 percent) Making it a very common and powerful item. The expert belt item adds a 1.5 multiplier to super effective moves, further enhancing damage output, and stacks with STAB in even those cases. Type enhencing items like the mystic water and miracle seed multiply their corresponding type's moves' base power by 1.2 (20 percent) Lastly, Gems multiply their corresponding stat's base power by 1.5 only once, after which it has been used up. Keep in mind that all these items are fairly common in competitive battling.
-Ability boosts-
There exists a myriad of abilities in the pokemon games, some of which will affect the damage multiplier. Some noteworthy abilities are the ones that increase your Stab by another 30 percent when your pokemon's life is below one third; like torrent, swarm and blaze. Sheer Force exchanges added hax effects on moves (such as para hax chances) for 1.3 multiplier. There are a ton of other abilities that play similar roles and knowing your way around them is the key to victory. The tinted lens ability mutliplies your base power by 2 when you hit with not very effective moves, NEGATING ONE resistance, btw.
-Weather-
rain and sunny weathers are special in the sense that they will affect the damage multipliers for some types. Basically, rain will boost water moves' base power and lower fire moves' base power and vice versa, in addition to all their other effects. In other words, water types almost always benefit from rain, but also pokemon who are weak to fire. Sun acts oppositely to it. Other forms of terrain changes will affect the game as well, such as the room that reverses the pokemons' defensive stats.
Knowing all this stuff is the first step in deciding what the build of your pokmeon will be before deciding its moves and its role in your team.