When dealing with Linux, root can mean two things; the first is the highest level in your directory. As in, keep clicking "up" while browsing your local files until the button goes gray and you are in your root directory.
The second, and probably most common, meaning is the main "administrator" account. This user account has complete control over everything that goes on on the computer. When you use YaST, you'll be asked for your root password (unless you are already logged in as root).
It is not a good practice to use your root account for everything. Rather you should set up a user account with less privileges to use for your day-to-day computing even if you are the computer's only user. This will make your box much more secure; should you ever get a virus, trojan, hacker, or script-gone-mad, there will be a limit to what the offending entity can do. It will also prevent you from doing something dumb; deleting an important system file or changing the permissions on a file and making it unusable or unsecured.