The main difference between an HMO plan and PPO plan is the flexibility and price.

HMO: You must choose a primary care provider (PCP) from a network of doctors. Your  PCP will refer you to other doctors and clinicians within that network for any specialized care you may need. HMOs generally have lower premiums and lower overall out-of-pocket costs than equivalent PPOs.

PPO: You don’t need a PCP. You can go to any doctor or facility you’d like without a referral, though you will pay less for services from doctors and facilities who are in-network. PPOs generally have higher premiums and higher overall out-of-pocket costs than equivalent HMOs. 

As always, remember to confirm that your provider accepts your insurance before you seek treatment to avoid paying unnecessary costs.