Penicillin is a type of antibiotic that was discovered in 1928 by Alexander Fleming. It is produced by certain molds and is effective in treating bacterial infections by killing or inhibiting the growth of bacteria. Penicillin is commonly used to treat conditions like strep throat, pneumonia, and skin infections. Since its discovery, penicillin has saved countless lives and revolutionized medicine. It is often the first choice for treating infections due to its effectiveness and relatively low cost. However, some bacteria have developed resistance to penicillin, making it important to use antibiotics responsibly.