• Poké Balls: Poké Balls are what you use to catch Pokémon. They can be found at PokéStops and bought in the Shop. Regular pokéballs can be bought with pokécoins from the Store. When you press on a Pokéball, a ring shows up around the Pokémon. A green ring means the Pokémon is easy to catch, while a red one means it's tougher to catch. The rings also change in size as you hold down a Pokéball.
• Great Balls: The next level in Poké Balls, Great Balls offer a higher catch rate, so if you're facing off with a rare or really strong Pokémon, put that Poké Ball down and whip out a Great Ball. That is, if you really want to catch of course. Great balls unlock at level 12 and are better at capturing pokémon, while ultra balls, which unlock at level 20 are even more useful for high-level pokémon. All three can be obtained at pokéstops once you've reached the right level, and r
• Ultra Balls: Exactly like the name sounds, Ultra Balls provide an even higher catch rate than Great Balls. If you come across a Charizard, don't even think; toss an Ultra Ball. These can be bought in the Shop once unlocked or found at PokéStops (if you're lucky).
• Master Balls: Ah, the elusive Master Ball, A.K.A. the Mewtwo catcher. These were available in the Pokémon Go beta but haven't yet appeared in the live version. Only time will tell. At any rate, Master Balls are the be-all-end-all of Poké Balls. They don't just have a high catch rate; they have aguaranteed catch rate. If you happen to come across a legendary Pokémon at some point (if Niantic adds them to the game), don't hesitate; use a Master Ball.

PRO TIP: Throw a curve ball!

• Curve balls aren't just stylish, they also increase a player's experience points if the technique results in a capture.
• To initiate a curve ball, move your finger in small circles on the screen while touching the ball and then toss it. It's still unclear if curveballs actually increase the chances of capturing a Pokémon, though they do definitely give you an XP bonus.