Strep throat is a bacterial infection. Clues that point toward it include a rapid-onset, painful sore throat, fever, tender swollen glands in the neck, and sometimes white patches or spots on the tonsils, usually without the runny nose, sneezing, or cough you would expect with a cold.
A cold-related sore throat is typically milder and accompanied by classic viral symptoms such as nasal congestion, a runny nose, and a cough. The presence of a cough actually makes strep less likely.
These signs only raise or lower suspicion; they cannot diagnose strep on their own. A doctor can confirm with a throat swab or rapid test, which matters because confirmed strep is treated with antibiotics. Do not take antibiotics without a diagnosis. See a doctor if you have strep-like features, and seek urgent care for trouble breathing or swallowing.