What does this Output error mean?

bad argument #2 to 'random' (interval is empty)

I don't know what that means, can someone tell me what it means?

GoldenPhysics's answer:

You have a math.random statement and the second number is less than the first.

That is, something like

math.random( 5 , 0 )

When explicit numbers aren't typed, it will frequently be from code that looks like this:

math.random( 1, #tab )

Which will cause a problem if tab is empty (since 1 > 0).