What we learn from our first steps as a Pokemon trainer is that some moves will work effectively against a Pokemon, while other kinds of moves will prove less effective. They are type matchups, a game mechanic that everyone who plays Pokemon knows. I remember reading a Pokemon guide before, and it says that Pokemon is like a game of rock-paper-scissors. The starters, in fact, are based around that game, seeing how water is effective against fire, fire is effective against grass, and so on. Originally, there were 15 types of Pokemon that existed. This changed some moves that we know today to be different, such as Bite.
When I played Pokemon Stadium for the first time in a few years, I was confused right off the bat seeing Bite function as a Normal-type move. But I realized that starting with Johto, Dark- and Steel- type moves would come into play. Magnemite, a classic example of one type-changer through the generations, is an Electric-type in the first games, then turns into an Electric/Steel type to maintain what it really is: a magnet. Depending on the type, Pokemon have certain weakness and strengths to other types. Another factor is dual types, where Pokemon have two types instead of the one. This can either open them up to more strengths, or weaknesses.
The Geodude chain is a very good example of this. Since Geodude, Graveler and Golem are Rock/Ground types, they have a weakness to Ground, Ice, Fighting, and Steel. That’s not all, though: both Rock- and Ground-types are weak to Grass and Water, making those types of moves doubly effective. Super-effective moves deal 2x damage, not counting STAB (Same Type Attack Bonus), making a Water- and Grass-type move deal a minimum of 4x damage, which is sure to be a one-hit KO.
Despite all this, there are some Pokemon that have absolutely no weaknesses at all. Sableye is one of the first Pokemon to have absolutely no weaknesses. Since it is a Dark and Ghost type, its weaknesses are covered up. However, its base stats aren’t too strong, so don’t expect a quick victory. Sableye can become invincible if you also have a Shedinja out on the field. If Skill Swap can be learned, hypothetically, Sableye can’t be touched at all, since its new ability would be Wonder Guard. Wonder Guard only allows super-effective attacks to touch the Pokemon, and since Sableye has none of these, it couldn’t be hit. But it’s just a theory; I don’t think either can learn Skill Swap. I forgot to mention type immunities, where one doesn’t affect the other, much like in real life. The classic example for this is Electric- and Ground-type moves. Lightning in real life is grounded by, well the ground, making the move completely useless. So one can say this game has applications in real life, but only to an extent. A good team, in my opinion, has moves that cover all of each other’s weaknesses. Build around that, and a formidable team is not too far from sight.