An antibiotic is a chemical that kills or stunts the growth of bacteria in the body. Antibiotics are used to help fight off bacterial infections. They are not effective against infections caused by viruses.
The term 'antibiotic' generally means a compound taken orally or injected, where antibacterial is more inclusive. For example, triclosan, the antibacterial in many soap products, is never ingested and is not referred to as an 'antibiotic'.