From Bulbapedia, the community-driven Pokémon encyclopedia.
Safari Zones are special preserves for rare wild Pokémon, found in several regions. Their mechanics are not too different from each other. All have a 500 entry fee, a certain amount of time to be spent within (except the Johto Safari Zone), and thirty Safari Balls, with which players may catch any Pokémon they come upon. The most important of their specific mechanics, however, is that Trainers do not initiate Pokémon battles with the wild Pokémon, but instead must catch them without harming them. The wild Pokémon within Safari Zones are capable of fleeing at any given time.
Safari Zones can be found in the following regions:
Johto's National Park shares some aspects with the Safari Zones; however, these are mainly in that it is a nature preserve for Pokémon. Its thrice-weekly Bug-Catching Contest also has several likenesses to the Safari Game. Kalos's Friend Safari area, located in Kiloude City, also bears some similarities with Safari Zones, differing in the available Pokémon for capture (which are dependent on the Nintendo 3DS Friend Codes of other players) as well as the permittance of unfettered Poké Ball use of any variety, as opposed to the restraint of strictly requiring Safari Balls.