From Bulbapedia, the community-driven Pokémon encyclopedia.
Safari Zones are special preserves for rare wild Pokémon, found in several regions. Their mechanics are similar to each other. Most have a 500 entry fee, a step limit, 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 battling them. The wild Pokémon within Safari Zones are capable of fleeing at any given time. The Johto Safari Zone has no step limit, while the Hoenn Safari Zone in Pokémon Omega Ruby and Alpha Sapphire has none of these mechanics, functioning instead like normal routes.
Safari Zones can be found in the following regions:
In the Generation II games, there is some data for a Safari Zone in Fuchsia City, but it was ultimately unused.
Johto's National Park is somewhat similar to a Safari Zone, being a nature preserve for Pokémon and having a thrice-weekly Bug-Catching Contest which shares several aspects with a 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 allowing Poké Balls of any variety as opposed to solely Safari Balls.
Unova is currently the only region to have neither a Safari Zone nor anything similar to or resembling a Safari Zone.