A Poké Ball is the standard capture item thrown at a wild Pokémon to catch it, with a 1 times catch rate multiplier, and the family also includes stronger and specialist balls such as Great, Ultra, Master, Quick, and Dusk Balls. The Master Ball catches any Pokémon without fail.
The standard Poké Ball has been the series icon since Generation I and multiplies the catch rate by 1. The Great Ball raises that to 1.5 times and the Ultra Ball to 2 times, and those three form the general progression of a playthrough: early game Poké Balls, mid game Great Balls, late game Ultra Balls for Legendary hunts. Premier Balls match the standard ball exactly and are a style choice.
The Master Ball is the outlier: it never fails, and most games give you exactly one, which most players save for a roaming Legendary or a Shiny they cannot risk losing, and many finish the game still holding it. Specialist balls trade raw power for conditions. The Quick Ball reaches up to 5 times on the first turn in modern games, the Dusk Ball is strongest at night or in caves, the Net Ball excels on Water and Bug types, the Dive Ball on underwater or fishing encounters, the Repeat Ball on species you already own, and the Timer Ball grows stronger the longer the battle runs.
Other balls serve other jobs. Luxury Balls speed up friendship, Heal Balls restore the caught Pokémon, and Apricorn balls in Generation II and its remakes offer odd, specific bonuses. Picking the right ball is free catch rate.
In play"Save the Master Ball, an Ultra Ball and some patience will get that Legendary eventually."