Editing WoW:AddOn programming tutorial/Introduction (section)

==== Functions ====
Functions are groupings of code that accomplish a specific purpose. There are numerous predefined functions provided by WoW (called API functions), or you can make your own user-defined functions. While there are multiple ways to create functions in Lua, the easiest to understand 
looks like this:

 <local> function ''function_name''(<zero or more arguments>)
    ... code ...
 end

*The <local> is an optional keyword that limits the visibility of the function to a particular scope. Scope will be covered in more depth shortly.
*The ''function_name'' is simply a name you make up so you can reference your function from other parts of your AddOn.
*The <zero or more arguments> are ways to pass information into the function. This is what gives functions their power. Each time you call the function, you can supply a different set of arguments and get different results based upon them.
*The ... code ... is where the work gets done in a function. Here is where you do calculations, comparisons, call other functions, etc. to get the task of the function done.
*The end simply marks the end of the definition of the function.

Note that this only defines or declares the function. The function is not actually run until some other piece of code references (or calls) it.

For more information on functions, see the [http://www.lua.org/manual/5.1/ Lua 5.1 Reference Manual] or [http://www.lua.org/pil/ Programming in Lua (first edition)]. Also see the [[Lua]] page which lists more Lua resources.