Can I get a over view of Ubuntu's sudo command and root user password?

Hi. I have very limited experience with ubuntu. I just decided to keep a version of Ubuntu handy for use and installed Bionic Beaver. My question is how does Ubuntu compare to Distros that have root user passwords? Doesn't the system need one for file permissions and security?If I get a SSH break in do they only have to guess my user password?

Thank your for your expertise!