From ZDoom Wiki
These specials are used to teleport one or more actors (often the player) from one section of the map to another.
|Note: When using teleport specials, make sure you are using Teleport Destination things and not Map Spots to mark the teleport locations. Teleport destinations have extra coding to make them work with the teleportation specials that map spots do not. Future compatibility is not guaranteed with maps that incorrectly make use of map spots in this manner.|