What's the difference between the Admin and Root accounts in Mac OS X?

• Root can do anything, without further authentication. There is only one root account and it is disabled by default.
• An admin user can do many things without further authentication, but can become root by authenticating with his own password. There can be any number of admin users.
• A standard (non-admin) user can only modify the contents of his own home folder, but can become and do admin and even root tasks by authenticating with an administrator's username and password, if he knows it.

Most security professionals recommend running with the fewest privileges as are necessary, elevating to the higher privilege only when needed, and returning to the lower privilege when the higher one is no longer needed.

Apple recommends running as a non-admin user all the time. It is the best for security, and is convenient too, since nearly all admin and root tasks can be done from a non-admin account, simply by authenticating with an admin username/password when prompted. I do admin and root tasks from my non-admin account all the time this way. My admin account almost never gets used; it has been months since I actually logged in to it.

If you are not already using a non-admin account, it's easy to switch: Just create a new account with admin privileges, and then remove admin privileges from your own account.

Any administrative user can get root privileges, so the idea is that since any malware would have the privileges of the user running it, a standard account would limit the damage to whatever that user could do.

The root user in a unix system has the power to do anything at will.

A user that can administer a Mac OS X computer has the ability to ask for privilege escalation in order to perform tasks that only root can do.

Running as an Admin user currently is only a danger to yourself accidentally messing things up. As hackers get better, there may be a possibility that they could exploit that power the admin user has to take over your computer.

Running as a standard user might prevent that threat since the standard user shouldn't be able to elevate their privileges.

If you're asking which you should use on a daily basis, make yourself an Admin and use that account.

If you follow K T's advice, be aware that you will not be following Apple's own security configurations guidelines. Apple says to use admin accounts only for tasks that really need to be run from them, and to keep admin accounts logged out at all other times. They even go so far as to say to "never check e-mail or browse the web while logged in to an administrator account".

Your choice.