Are macbook 10.6 OS discs available, I have lost mine?

Have receintly aquired MAcbook, can't find the original OS disk anymore. Not familiar with Mac's, trying to load software, getting prompted to input password. Don't know it. Have found several hacks, sound suspect to me. If I crash it, can I find Mac 10.6 OS disc to reload??

Terry Turnbull

Nanaimo BC