If index is a number, returns all items in the list from that number onwards. Otherwise index must be the string "#", in which case it returns the number of items in the list. This can be used to simulate the behaviour of the old "arg" feature in Lua 5.0, for use with variable numbers of arguments passed to a function.
function f (...)
print (select ("#", ...)) --> 4
print (select (2, ...)) --> 20 30 40
end -- f
f (10, 20, 30, 40)