jail is where you are sent if you get caught doing a crime. You are put in jail for a diffrent amount of time, depending on the crime. the less brave required the less time in jail. dont worry if you get caught and it says your in jail for 120 minutes. someone will probable bust you out within a few minutes.
Fed Jail is much worse than jail. if you are put in fed jail, you cant play for blank amount of days. there is no way to get busted out. you must serve your whole time.