Concepts of plugin features
Everything in the Worlds plugin is controlled by flags. Some flags are build, pvp, damage, fly, command, for example.
There are also different types of flags. Some flags like permission or game mode are set to a custom value. Most other flags are either set to true/false for enable or disable, or provide control list functionalty and can therefore be set to true/false/white/black (white for whitelist, black for blacklist behaviour of the control list).
Flags can be set on the default level (used when there is nothing set in a world) or in an individual world (overwriting the default value).
Control lists contain a set of things you want to control, e.g. block ID's at the build flag or command names at the command flag. When a flag is set to 'white', the control list will be used as a whitelist and only blocks which are added to the list may be placed/broken. When set to 'black', it will be used as a blacklist, so e.g. commands which are added to the list may not be executed in this world.