An antibiotic is a type of medicine that helps fight infections caused by bacteria. It works by either killing the bacteria or stopping them from growing. Antibiotics are commonly prescribed by doctors to treat illnesses like strep throat or pneumonia, making it easier for the body to heal. However, they are not effective against viruses, such as the common cold or influenza. It's important to use antibiotics responsibly. Taking them when they are not needed can lead to antibiotic resistance, where bacteria evolve and become harder to treat. This is why it's crucial to follow a doctor's advice and complete the full course of antibiotics when prescribed, ensuring that the infection is fully cleared.