The unit of execution of Lua is called a chunk. A chunk is simply a sequence of statements, which are executed sequentially. Each statement can be optionally followed by a semicolon: 

	chunk ::= {stat [`*;*`]}

There are no empty statements and thus '=;;=' is not legal.

Lua handles a chunk as the body of an anonymous function with a variable number of arguments (see Function Definitions). As such, chunks can define local variables, receive arguments, and return values.

A chunk may be stored in a file or in a string inside the host program. When a chunk is executed, first it is pre-compiled into instructions for a virtual machine, and then the compiled code is executed by an interpreter for the virtual machine.

Chunks may also be pre-compiled into binary form; see program luac for details. Programs in source and compiled forms are interchangeable; Lua automatically detects the file type and acts accordingly.