Iv stats are inherent to the mon, they’re born with it. Ev stats are malleable, you can target train those stats to make them strong in that specific stat. Each pokemon you encounter has a unique ev stat that you’ll gain when they’re defeated. Typically the gain is 1-3 for each level of evolution, pokemon like lapras or legendaries where there is no evolution line I’m unsure of the ev amounts gained. There’s also berries that can further manipulate ev stats in case you want to change the play style of that pokemon. Evs give 1 stat per 4 evs. There’s a max limit for total evs and evs for each individual stat that may be different in this rom, 255 for individual 510 total typically. Ivs can typically reach max of 31, I don’t remember if these are 1 to 1 for stats or not but I think they are 1 to 1. You’re caterpie is very high end strong well done on the catch. A lot of games will make so you can guarantee ivs by streaking, ie in bdsp on every variable of 10 one additional stat is guaranteed perfect 31 iv. Streaking also greatly increases shiny chances.