EVs (Effort Values)
EVs are a secondary value that adds to the main stats of your Pokemon. You gain EVs by defeating Pokemon in the wild. Each Pokemon gives 1 or 2 EV points for a specific stat. You can spend your EVs on the stats that you want to by click on the EV tab of your Pokemon.
You can spend up to a maximum of 510 total EV Points and a maximum of 252 total EV Points for an individual stat.
At level 100, your Pokemon gains 1 point in their stats for every 4 points in their EV stat. So if you have 252 EV points in Attack, it will raise your Pokemon’s attack stat by 63 points at level 100.