Lua Fundamentals

Lua is a dynamically typed scripting language designed at PUC-Rio, the Pontifical Catholic University of Rio de Janeiro, with development starting in 1993. It is small, fast, and built from the start to be embedded inside a host application written in C or another language. You rarely run a bare Lua program the way you run a Python script; more often, a game engine, a proxy server, or a text editor loads Lua as its scripting layer and calls into it.

That embedding design shapes everything else about the language. Lua has a tiny core, a simple C API for the host to call Lua and for Lua to call back into the host, and a small standard library. Features that other languages bake in — classes, modules, exceptions — Lua builds instead from a few general mechanisms: tables and metatables. Learn those two well and most of the rest follows.

Values and types

Every Lua value has one of eight types: nil, boolean, number, string, function, userdata, thread, and table. nil means "no useful value here." number covers both integers and floating-point values as two subtypes of the same type, a distinction Lua has kept explicit since Lua 5.3. userdata is how the host application exposes its own C data structures to Lua code. thread is the type of a coroutine, not an operating-system thread.