minetest.register alias

Description
is converted to  by the engine. This means that if the engine finds nodes with the name  in the world the node with the name   is used instead.

This is useful to maintain backwards compatibility.

There are also other cases like map generation where aliases are used. The  command also looks for aliases when adding the item to the players inventory.

Example 1
The map generator of the engine uses some nodenames for the output that are not registered. The default game registers aliases so the engine knows wich nodes to place there:

Example 2
In the versions of Minetest before 0.4 the nodenames havent prefixed the modname. To be able to load old maps with the new versions the legacy mod adds aliases to convert the nodenames: