Introduction
Comitting several actions inside the game might lead you towards getting locked up in jail.
Actions such as; Criming, GTA, shooting world bosses/NPC's or trading drugs.
While you're in jail your actions will be limited.
Unless you get busted or bought out of prison buy another gangster you won't be able to leave the jail unless your jail time ended.
Busting
Players can decide to bust out other players from jail.
However, there is always a chance that if you fail to bust the other player that you might end up in jail yourself.
Buying out
Players can decide to buy out other players from jail.
Money spend on buying someone out of prison will not go towards the player.
Isolation
In very rare cases you'll see players who are in ISOLATION.
When a player is in ISOLATION they do not gain any stamina, you also won't be able to bust/buy them out of jail.