When should we use return and how to use it?

Hi, I would like to know when to use return. The only thing I know where to use return is a simple add function, like this:

function addnum(num1,num2)
    return print(num1,num2)
end

addnum(1,2)

Although the same results can be seen without return:

function addnum(num1,num2)
    print(num1 + num2)
end

addnum(1,2)

I would appreciate it if someone could tell me when to use return and how to use it.

Thanks to those who helped!