What do the letters RFC of a Guerrero State driver's license mean?

RFC (Registro Federal de Contribuyentes) is the Federal Taxpayer's ID issued by Mexico to all of it's citizens.

In Mexico, two last names are used, the father's and the mother's.

So for example for Manuel Guerrero Avila, born on February 10th, 1985; the RFC would be:

GUAM850210, being GU - the first two letters of the first last name, A - the initial of the second lastname, M - the names's initial and 85 - the year, 02 - the month and 10 - the day that he was born.