This and many more tips are located on our Pokémon Go tips & Tricks page.
So what is IV?
IV stands for Individual Value and this value stays constant even after evolution. The values for IV range from 0-15 and can be calculated from CP, HP and Dust with a calculation we’re not entirely sure of yet.
As previously stated the IV seems to determine the max CP you can obtain so the higher IV means the higher possible CP.
Still not clear take a look at this IV Calc for possible clarification.
Highest CP may not always be the best because high defensive points but low CP might be a good gym defender. So don’t go getting rid of everything with a low IV score just yet.
It was found by RedBeard that it made life easier if you renamed the pokemon according to their IV because IV is not displayed in Game. This also gives alternate sorting and makes decisions to transfer easier to determine. See pic. The CP is the % value below the pokemon.
An IV list can be generated using PokeAdvisor