Mods are a way of modifying/expanding the WarLight core gameplay beyond what is possible using the built-in configuration options. They are currently available as a preview by using WarLight's Unity client, which is only available to members.
Mods are coded in the programming language Lua which, after uploading it to WarLight, gets embedded into both the WarLight server and the client. When joining a multi-player game with mods, the WarLight client will automatically download and run the code for that mod. No installation is required by end-users to use mods, they simply join or create a game that has mods enabled.
See the Mod Developers Guide for details on how to get started making your own mod.