Capture the flag is played on some sort of playing field. Whether indoor or outdoor, the field is divided into two halves, known as territories. Players comprise two teams, one for each territory. Each side has a "flag" which is most often a piece of fabric, but can be any object small enough to be easily carried by a person. The flags are generally placed in a visibly obvious location at the rear of a teams territory. The object of the game is for players to make their way into the opposing team's territory, grab the flag and return with it to their own territory without being tagged. The flag is defended mainly by tagging opposing players who attempt to take it. Within their own territory players are "safe", meaning that they cannot be tagged by opposing players. Once they cross in to the opposing teams territory they are vulnerable.
In another, more difficult version, the flag is hidden in a place where it can only be seen from one angle. It also might have some challenge involved. For example, the flag could be hidden in the leaves up in a tall tree, and the players have to see the flag, then knock it out.
Different versions of Capture the Flag have different rules both for handling the flag and for what happens to tagged players. A player who is tagged may be eliminated from the game entirely, be forced to join the opposing team, or be placed temporarily in "jail." The jail is a predesignated area of the group's territory which exists for holding tagged players. It is usually located a good distance from the flag in order to minimize the possibility of simultaneous flag grabs and jail breaks. While tagged players may be confined to jail for a limited, predetermined time, the most common form of the game involves the option for a "jailbreak." In this version, players who are tagged remain in jail indefinitely. However, players from their own team may free them from jail by means of a jailbreak. Jailbreaks are accomplished by a player running from their own territory into the enemy's jail. Such action may, depending on the rules, free all jailed players or simply those who are physically touched by the one performing the jailbreak.