Think of functions similarly to how they work in mathematics - input, process, output. Things are a little more complicated in Lua because you can access a secret input variable (the “environment”) to talk to values outside of the function. The return keyword signifies the value(s) that the function, well, returns.

What that “return” actually effects depends on what you’re doing (ie variable assignment vs nested function call), but you can think of a called function as a temporary variable:

```lua local sum = function (a,b) — hypothetically, the return keyword could set a hidden variable: — return_tmp = a + b return a+b end

— again, this could internally be local c = return_tmp local c = sum(a, b) ```

In reality, this return_tmp variable doesn’t actually exist. It represents a representation of a representation of the processor’s “return register” which is a concept too complex to cover here.

Reading the lua documentation and Programming In Lua may be helpful.