A nest ball is an item in the video game series "Pokémon" that is used to capture wild Pokémon during battle and add them to a player's roster. It is one of many such items, which are called pokeballs.
When capturing a wild Pokémon, there is always a chance that the target ends up escaping. Nest balls, unlike other pokeballs, are specialized to preferentially capture wild Pokémon that are lower in level. Levels are a measure of the Pokémon's battle experience. Nest balls work best when attempting to capture Pokémon with a level lower than 19. They are slightly better than standard pokeballs at capturing Pokémon of levels between 20 and 29. They capture at the standard rate when the Pokémon's level is 30 or above.