From Team Fortress Wiki
Freeze Tag is a Team Fortress 2 gameplay modification based around the concept of the children's game Freeze Tag. It is a Sourcemod plugin and is incorporated alongside regular game modes such as Control Point and Payload.
In the Freeze Tag game mode, you attempt to complete the objective of the map you are on as normal (be it pushing the cart or capturing points).
The only difference is when someone dies in this game mode, they freeze in the place where they die for a certain amount of time. Players can be unfrozen if a team member comes to resuscitate the player by standing within a certain perimeter of the player. Once the unfreezing is complete, the player may resume normal gameplay from the spot they are revived. If someone is frozen their name will be displayed in the upper left corner showing how much longer players have to stay within their perimeter.
After a certain amount of time, if nobody rescues a player, they will be killed and respawn as normal.
Depending on the version of Freeze Tag being played, there will be one of two effects whilst frozen. One possible effect is that the player will only be able to revolve around and use Special taunts. The second possible effect fully stuns the player, leaving the player unable to move or attack. Calling for Medic while in this state will instead make the player call for help.