CP, or Combat Points, is a measure of how effective your Pokémon is in battle. It pays to keep and evolve only the best Pokémon you find. In general, you want higher CP Pokémon to evolve over lower CP Pokémon, but just because a Pokémon has a high CP doesnt mean its actually very good.
What should I do with my low CP Pokémon?
CP stands for combat power — the higher the CP, the stronger the Pokémon will be in battle. In general, you want to trade away your low-value Pokémon so you can build up your stronger ones. You can only use the candy you receive for transferring a Pokémon on another of the same type.
Why is umbreon so weak in Pokemon go?
while not including Abilities (like Synchronize) nor movesets that would buff/debuff/affect status (like Curse, Toxic, etc.). Thus, Umbreon is a defensive poke with little battling use in PoGo because it can only access offensive moves and it lacks its key ability, Synchronize, to further remain defensive.