When I "Click the lock to make changes" it won't accept my password. I am an Admin. Is his password different to my login one?

I am the Admin on my iMac (using macOS Big Sur) and need to allow some system accesses and to add another Admin account. When I click on the padlock to make changes it doesn't allow my password. Is this different from the Login password and, if so, how do I change it as I don't know what is is?