@cantelopeavocado has a nice explanation, permit me to compliment hers by breaking it down in a slightly different manner. For admissions purposes, applicants need to fall into one of three categories in order to receive a secondary:
IS - by standard definition
OOS - must be current resident of AZ, CA, ID, OR, or UT
OOS - must have connection to Nevada, which will be judged using the aforementioned criteria (graduated from Nevada high school, primary family member in Nevada, etc.)
The UNLV School of Medicine's core mission is to increase the physician workforce in Nevada, and we felt the best candidates to fulfill that mission will be either local, regional, or have some other ties to the area.
I hope this makes sense.