HMO stands for Health Maintenance Organization.  This is a network based around a group of doctors that have contracted with the insurance company.  HMO networks are often based around a regional hospital, generally will not cover out-of-network care except in emergency situations, and require that you live or work in the service area to be eligible for the plan.  Most HMOs focus on prevention and wellness.

With plans that utilize an HMO network, you can usually expect lower monthly premiums and lower out of pocket cost in exchange for more restrictions on which doctors you can.  You will often times also need referrals for specialist.