Combat Power (CP) indicates how well individual Pokemon perform in battle. In Pokemon Go, there is no stats or abilities such as the Attack stat and the Defense stat (These are hidden values known as base stats, and CP is decided based on those values). Unlike other Pokemon game series, each Pokemon has only CP and Hit Points(HP). The higher the CP value of individual Pokemon, the more powerful the Pokemon is.
Catching Wild Pokemon with Higher CP
When you find wild Pokemon, the CP value appears above the Pokemon. They are assigned the different CP value. For example, if you encounter two Zubats, they may not have the same CP. TO raise Pokemon faster, you want to capture Pokemon with the higher CP value.
Trainer Level and CP
As your trainer levels up, the CP value each Pokemon can have increases. That means your trainer levels is important for growing the Pokemon.
To increase the CP and HP value of Pokemon, powering up Pokemon using Stardust and Candy is required. You can get these by capturing Pokemon, hatching Eggs, or transferring Pokemon to Professor Willow. Candy is specific to each Pokemon and its first- and second- evolution Pokemon. To acquire candy for the Pokemon you want to grow, catching same Pokemon as much as you can is essential.
Using Candy to Evolve.
Evolving allows the Pokemon to have the much more CP value. Evolution requires a lot of candies relative to the number needed to power up.