"Does anyone know how I can learn the concepts of competitive?"

I've been playing pokemon games for about 4-5 years now, and I've been playing around with the idea of giving competitive a try. Does anybody know a good source or website/ analysis video that would help me learn how to build a competitive team? Or if you can just explain some things in the comments that would be helpful too. I understand how EVs/IVs/Natures and things like that work, but I just don't get where I would start with understanding the specific strategies behind building a team. Any help will be greatly appreciated. Thank you and have a good day via /r/pokemon https://ift.tt/dHgqNCJ