The **Legacy mod** is the default mod shipped with `ET: Legacy <http://www.etlegecy.com>`_. It supports server-side modifications via the `Lua <http://www.lua.org/>`_ scripting language.
If present, the embedded Lua 5.3 interpreter will load user-defined scripts from the Legacy directory. It also provides an "et" library of function calls for Lua that allow access to the server engine, and provides callbacks so a server side mod may trigger on specific server events.
For more information about Lua, check out the `Reference Manual <http://www.lua.org/manual/5.3/>`_, the online edition of the book `Programming in Lua <http://www.lua.org/pil/>`_ or the `Lua-users wiki <http://lua-users.org/wiki/>`_.
If you want to see some ET-specific Lua examples, you can check the `ET Legacy Lua scripts <https://github.com/etlegacy/etlegacy-lua_scripts>`_ repository.