CTF or Capture the Flag is a game mode where in the objective is to steal the enemies "flag" (sometimes replaced in other games with items such as a briefcase of intelligence) and to return it to your own teams base.
The goal of both teams is to steal each others' flag and return it to their own. However, if both teams steal the flags, then no one can score.
For example, if Team A stole Team B's flag and returned it to their own base, they would score. However, if Team A stole Team B's flag, and then Team B stole Team A's flag before the carrier from Team A could return the flag to his base, then no one would score until at least one of the flags was returned.
The returning of flags is slightly different in each game. Standard practice is for a player to "drop" the flag once they are killed, and an opponent must touch the flag for it to be returned to their base. However, in Team Fortress 2 once a flag is dropped, it remains there for a pre-set amount of time (usually 60 seconds) until either the timer runs out (in which case it is returned to the base) or an opponent touches the flag and picks it up again, resetting the timer until it is next dropped and it will continue to count down from 60 seconds once more.
It is unclear what mechanic for returning the flag Global Agenda intends to introduce as of yet. However, in at least some versions of this game style the 'flag' is actually a giant robot that the capturing player needs to drive back to their own side.
Normally CTF maps are symmetrical, maybe except for slight differences in appearances or navigation, but the play-testing should make sure the map is fair.
Once someone has managed to capture the enemy flag, it is in their team's best interest to help them back to their base while sustaining as little damage as possible. This is because every time the flag is dropped, there is a chance the enemy may return it, severely hampering a teams ability to score.
If your own flag has been stolen, there are two common tactics employed to combat this.
Capture the Enemy FlagEdit
In this tactic, a team will rush the enemy base in an effort to capture their flag, thus rendering them unable to score. The thinking behind this is also that most of the enemy team will be preoccupied in having just caught your own flag, and thus the base should be relatively defenceless. Teams can then choose to camp in the enemy's own base waiting for their flag carrier to return and kill him, returning the flag, although this presents a major risk as the enemy's flag is still inside their own base!
Another option is to then flee the enemy base via the most popular route, hoping to engage the enemy flag carrier on the way back to your base. However, if neither team encounters the other, then a stalemate is introduced.
Stop the Flag CarrierEdit
This tactic involves stupidly large amounts of firepower and most probably death for a lot of your team - but will also probably work given enough planning and co-ordination.
If the enemy base is a long way away and your flag has just been stolen, you know the flag carrier is in your base - giving you the upper hand due to your re-spawn being in close proximity. Knowing this, a team can literally just throw everything they have at the flag carrier and his escort, in the hope that sheer power and numbers will kill them, and thus drop the flag inside your own base; this also making life hell for the enemy to try and retrieve it once more.