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, a series of distinct areas with different wild Pokémon in each, and thirty Safari Balls, with which players may catch the 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 in Pokémon Omega Ruby and Alpha Sapphire the Hoenn Safari Zone has none of these mechanics, its areas functioning instead like normal routes. Pokémon: Let's Go, Pikachu! and Let's Go, Eevee! effectively do not have a Safari Zone; the area that used to be the Safari Zone is replaced with GO Park, while the zoo area in front is referred to as the "Safari Zone".
Safari Zones can be found in the following regions:
In the Generation II games, there is some data for a beta 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 wild Pokémon (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. The Pal Park in all Generation IV games bears some superficial similarities to a Safari Zone, being a special area where only a specific type of Poké Ball can be used, featuring possible Pokémon species that otherwise cannot be found, and where the player cannot battle the Pokémon found there. (Additionally, in HeartGold and SoulSilver the Pal Park is placed in Fuchsia City where it replaces the Safari Zone.)
Unova, Alola, and Galar have neither a Safari Zone nor anything similar to or resembling a Safari Zone.