As with other Pokémon games, each of the characters in Pokémon GO's massive roster have their own strengths and weaknesses. These are denoted by their type, which can range from Fire, to Fairy, and even Dragon.
This is an incredibly important element of Pokémon GO, especially when it comes to the Gym and soon-to-be-released friend battle systems. Even if the Pokémon you're battling has more CP and a larger health pool, you can take them down as long as you take advantage of their weaknesses.
Below are charts that display each of the major strengths and weaknesses of every Pokémon type.