Short answers, pulled from the story.
Antibiotic literally means opposing life, from the Greek roots anti, meaning against, and bios, meaning life. The term was first used in 1942 by Selman Waksman and his collaborators to describe a substance produced by a microorganism that is antagonistic to the growth of other microorganisms.
Sir Alexander Fleming discovered penicillin in 1928 after noticing that spores of a green mold, Penicillium rubens, killed or prevented the growth of bacteria on one of his culture plates. He named the antibacterial substance penicillin but could not develop it further without trained chemists.
Antibiotics are active against bacteria, not against viruses such as those causing the common cold or influenza, and not against fungi. Drugs that inhibit viruses are called antivirals, and drugs that inhibit fungi are called antifungals.
The earliest known use of antibiotics was found in northern Sudan, where ancient Sudanese societies between 350 and 550 CE consumed antibiotics as part of their diet. Chemical analysis of Nubian skeletons showed high levels of tetracycline, likely from beverages brewed with grain fermented with the bacterium Streptomyces.
Nearly 5 million deaths each year are associated with antimicrobial resistance globally. Global deaths directly attributable to antimicrobial resistance numbered 1.27 million in 2019.
Antibiotics target bacterial functions or growth processes. Drugs targeting the cell wall, cell membrane, or essential enzymes kill bacteria, while protein synthesis inhibitors such as macrolides and tetracyclines usually only inhibit further growth. Narrow-spectrum antibiotics target specific bacteria while broad-spectrum antibiotics affect a wide range.
Researchers are developing phage therapy, which infects bacteria with viruses, fecal microbiota transplants with cure rates around 90% for C. difficile, antisense RNA that silences resistance genes such as the S. aureus mecA gene, and reprogrammed CRISPR-Cas9 systems that target bacterial resistance and virulence genes.