There are two events involved with teleports, Warp and Warp Target. "Warp" is the event you enter to teleport. "Warp Target" is the event you teleport to. The "id" of the two events determines which Warp Target you go to. If you enter a Warp with id5, you will go to a Warp Target with id5.

Good JCS help site.
Another good JCS help site, more advanced.
Article: Multiple warp targets with the same id.