Herpes infections occur when the virus enters through small openings in the skin and mucous membranes of the mouth, nose, and genitals. Once inside, it infects nerve cells and remains there for the rest of its life cycle, periodically reactivating to cause an infection. During latent periods, the virus is dormant and symptom-free, but it can reactivate due to triggers like stress, illness, or changes in the immune system.