Caterpie is a pure bug type pokemon. Obviously, it is a green caterpillar. It was caught by Ash easily in the wild.
In Pokemon Go, its max CP is at 393. It can learn Bug Bite and Struggle as fast moves while Struggle is its ONLY charge moves. It can be obtained as well by hatching from a 2 km egg. If used as a buddy, it needs 1 km distance to get one Caterpie candy.
As a bug type Pokemon, it is weak against flying, fire and rock Pokemon. It is super strong, however, against fighting, grass and ground types. It is just a bug type so fairly weak. This is still caught for Pokedex entry. Then again, it is very useful especially when you are trying to increase your XP for mass evolution. It costs only 12 caterpie candies to evolve to the second level and it is fairly common so it is easy to collect the candies.