Penicillin is the first naturally occurring antibiotic discovered and the first to be used therapeutically. This means that it is a substance that can kill or inhibit the growth of certain types of bacteria. It is generally associated with treating infections such as diphtheria, meningitis, pneumonia, and more common ones such as strep throat. It can be taken orally as a liquid or pill, or you can take it through a type of shot. It is a favorite drug for doctors to prescribe. .
Penicillin was discovered in 1928 by a Scottish Physician, Alexander Fleming. Before this time people new little about germs and bacteria, they would never wash out their wounds or use what we consider proper cleanliness. But, Fleming noticed the connection between a dirty wound and it later becoming infected. So, he started doing some work of his own. He placed bacteria and a substance from which it could grow off of into a petri dish and covered it. He accidentally left the lid off of one of the dishes and discovered some unusual fungus growing in it. Fleming observed that where this fungus grew the bacteria had ceased to exist. He then correctly reasoned that this fungus must kill the bacteria and he identified it as Penicillin.
Although Fleming's discovery of penicillin was exciting he could not find a way to make it useful to the public and he quit doing research. Then Howard Florey comes along and starts doing some testing with it. Finally in 1940 he had found a way to make the drug useful for humans and just in time for World War 2. Florey's work with penicillin ended up saving millions of lives and earning him the Nobel Prize for Medicine in 1945. Producing enough Penicillin was still a problem, but with the pressure of the war there was such a demand for the new wonder drug that it did not take long for pharmaceutical companies like Eli Lilly to learn how to up-scale production.
Penicillin is not something that you would necessarily connect with having an impact on Technology.