Need apple mac help p?

A while ago I got an update the apparently needed my password. Hadn't happened before in a year. I don't seem to have it somewhere, I tried every1 I knew. I had to shut it off and turn it back on. Now I got an update again with it but luckily it didn't restart. Is there someplace with forgot password/reset password? except I don't remember it and I know what I would have used. None of them worked. It's the very main password to log on.