linux - Why "sudo -s" change to root user without asking for password

Question

When I type in "sudo -s" in the command line, I changed to root user without typing in any passwords. I'm confused why this happened. From my understanding. Can someone explain that?

Answer 1

Because this/previous session you was root also.

lets say if you entered as root, sudo -s - no action. Or you created session, entered as root, closed for example ssh connection and entered once more (during 5 min), the result, you still stay as root