The exit portal always generates at the coordinates 0,0, and remains deactivated until the ender dragon is killed.
The exit portal looks similar to the end portal but differs in its design. Instead of a frame of end portal frame blocks, it has a 7-block wide bowl-shaped frame of bedrock, and a central pillar of bedrock with a torch on each side. A dragon egg generates atop the portal upon defeating the ender dragon.
There are 16 end stone blocks, one under each outer bedrock block, and if mined they will regenerate when the ender dragon is defeated or respawned.
If a player goes through the exit portal, the credits will roll if entered for the first time, after which they will go to their spawn point in the Overworld. If an entity that isn't a player goes through, it will be sent to the world spawn location. The ender dragon will fly to the fountain from time to time, and spew Dragon Breath (Ender Acid in the Legacy Console Edition).
The portal is made up of the same block and block entity as the End portal.