What is the main use of penicillin in medicine?

Penicillin is a class of antibiotic medications. Penicillins treat bacterial infections like strep throat, ear infections, and urinary tract infections. They work by attaching to and damaging the cell walls of bacteria. Types of penicillin include penicillin V, penicillin G, amoxicillin, and ampicillin. Penicillin antibiotics come in oral form (pills or liquid you swallow) and IV form (liquid that a provider injects directly into your vein).

Source: Cleveland Clinic