Logged in as a USER
Logged in as ROOT
User with sudo ability
Anyone logged in as a User has limited access, cannot change the system or destroy other users data. Safe for daily operations and better for security
Anyone logged in as Root has unlimited access, can change the system or destroy other users data. Dangerous for daily operations and bad for security
In Ubuntu a person with Root access can run in User mode and then shift up when needed to Root for each operation using the sudo command
On any OS it is best not to do your daily work logged in as Root or Administrator
The sudo command is a security upgrade on several Linux distros