Worlds, in Tribal Wars 2, is another word for game servers. Every world have the same fundamental functions - but there is some difference to the settings, such as world speed, unit speed, tribe limit etc.
A player can play on multiple worlds with 1 account, however it is forbidden to play on the same world with 2 or more accounts.
There will be different servers, with different settings. Below you can find a list of all worlds, and their settings.
To view an explanation of the settings, please look at the settings overview.