A throat culture is a test to identify bacteria or fungi that may be causing a sore throat. It involves using a cotton swab to collect a sample from the back of the throat and tonsils, which is then placed in a sterile container and sent to a lab. At the lab, the sample is cultured to see if any bacteria or fungi grow, indicating an infection. Throat cultures are performed when a sore throat is present to determine if it is caused by streptococcus, diphtheria, gonorrhea, or other infections.