Over the course of time i have forgotten the use of returning?

Functions are bits of code that you would like to reuse.

local function foo()
	print("hello")
end

This function will print hello to the console.

When we use a function, we call it a function call.

foo()

This is a function call.

Function calls are expressions. Meaning they will evaluate/simplify to a value. In terms of function calls, they will evaluate as whatever the function returns.

local val = foo()

This will print "hello" to the console, but the value of val will be nil. Because foo() does not return anything. And nothing in Lua in nil.

If we want the function to not evaluate as nil then we use return

local function foo()
	print("hello")
	return 5
end

local val = foo()

The value of val is now 5.

This is helpful because we can abstract tasks with multiple terms like this

local function sum(a, b, c)
	return a + b + c
end

local val = sum(1, 2, 3)

In this case val is 6. Because 1+2+3 is six.