Su switches you to the root user account and requires the root account's password. You can also use it to switch to any user account.

Sudo runs a single command with root privileges. It does not switch to the root user or require the root user's password. In order to execute sudo a user must be added to the sudoer's file. (The user created during the installation of Linux is automatically added to the sudoer's file.)

What’s the Difference Between Sudo and Su in Linux?