More information on the tour look through the its site. The following is culled from the main page:
An omnium is a set of races in which riders compete for points in each event, and final placings are determined by total points from all events. Bonus points are awarded for completing more than one event. An omnium differs from a stage race in that riders don't have to finish all races in order to be eligible for prizes. The bonus points awarded for finishing multiple races, however, give those racers an advantage in the overall scoring.
The Tour of Socorro is an omnium combination of the South Baldy Hill Climb and the Cerrillos del Coyote. For a detailed description of how scoring will be done, and how the omnium will figure into the overall NMORS standings, please see the Awards section.