- Wikipedia: Lua
Lua 5.1.4 is the current and main programing language behind scripting on Roblox. Lua was designed by Roberto Lerusalimschy, Waldemar Celes and Luiz Henrique de Figueiredo. The latest stable version of Lua is Lua 5.3.5, but Roblox uses Lua 5.1.4. Roblox uses an altered version of Lua, known as RBX.lua, which includes Instances and a bunch of custom Data types made in C++.
Lua uses lines of code to tell the game what to do at a certain time or place. It can be used to express ideas to other people, mostly in games called script builders. Using Lua can be hard or easy depending on one's scripting skills.