In Pokémon GO, whenever you check your Pokémon’s stat page, you always see numbers under the categories, CP and HP but what do they really mean? CP and HP are both abbreviations, respectively, they mean Combat Power and Hit Points. Now, Hit Points are standard in RPGs and even other genres, if you play videogames, you know that HP is your health and if it ever depletes to 0, it’s game over or at the least you’re dead.
CP, or combat power, is a measurement of how effective in combat your Pokémon is. CP calculates the Pokémon’s HP, attack, defense and level to produce that number. You may notice though that you can’t find where attack, defense and level are in your Pokémon’s status page, Attack and Defense are actually hidden stats and you can only get a general estimate of both by using the appraise function. Level, however, can be seen although it’s not indicated. That semi-circle above your Pokémon that fills as your power-up or level-up your Pokémon is it’s level relative to yours, and you cannot power-up your Pokémon when that semi-circle fills up.
When battling, comparing CP is always a good indicator if you can take on the enemy Pokémon if your type matches are neutral. After every battle make sure to fully heal your Pokémon’s HP with potions (super and hyper are necessary at high levels) and revive any fainted Pokémon you might have. Now that you know what HP and CP are, you can use both to judge whether you can take on an enemy gym or reinforce an ally gym.