Self-explaining, isn't it? Each world has its own tablist, so players can't see players that are in other worlds. You can define groups of worlds so those worlds share a combined tablist.
Spanish video tutorial by maxmar628:
== Getting started ==
Place the PerWorldTablist.jar file in your plugins directory.
Reload/Restart/Start your server.
Handle your permissions.
Have fun!
== Commands and Permissions ==
Command
Function
Permission
/pwtl <reload>
Reloads PerWorldTablist
pwtl.reload
/pwtl <list/glist>
Shows a list of all players that are in your world/on the server
pwtl.list/pwtl.glist
Players with this permission will see all players
pwtl.exempt
Aliases for pwtl
/perworldtablist
/perworldtab
/pwt
== Configuration ==
The configuration is self-explaining.
== Compatibility ==
This plugin should break several vanish-plugins, because it shows/hides you/other players when u change the world. Compatible vanish-plugins: