list

This will list all currently loaded worlds with name and UUID. If Minecraft Forge is present, the world provider name will also be shown, as well as all unloaded worlds that available for loading.

Example on Spigot and Glowstone:
Example on Cauldron:
create

Dynamically creates a world and load it. It uses standard bukkit API to create world so if the a world save is exist in save directory, the world will be loaded from file system; in this case, some but not all world settings (such as world seed) will be read from save, instead of command line options of this subcommand.
See on-line usage message for more information.

load

This subcommand is available only if Minecraft Forge is present. It loads worlds that registered in Forge but currently unloaded. Use 'world list' for currently unloaded worlds.

unload

Unload a world. Note some implementations such as Cauldron may allowing you to unload overworld, but the server software will not functioning correctly after that; while some other such as Glowstone appear to be fine with overworld unloaded. Forge registered worlds can be loaded again using 'load' subcommand, 'switch' subcommand or in-game portals, so you may use it to unload currently unneeded worlds (but not overworld!) to save memory on Cauldron.

control

Display or change world properties.

save

Save one or more worlds to file system.

switch

Teleport yourself or a specified entity to another world. If the world is currently unloaded but available from Minecraft Forge world registry, it will be loaded first.
The default teleport destination is the spawn point of the world; option '-c' can be used to use current player position instead, inter-world movement factor (such 1:8 for Nether) is considered in this case; option '-p' can be used to specify a coordinate to teleport to.