What is antibiotic resistance? How does it work?

Antibiotic resistance is when an antibiotic is used, where most of the bacteria is killed off, but some are left from having the ability to resist the antibiotics effects on it, which are the preferred selection, so they begin to multiply. This resistant bacteria occurs either due to the overuse of antibiotics for unnecessary reasons, like for the common cold, or because of natural causes. For example, bacteria can become resistant because of either a genetic mutation or getting help from another bacterium. This mutation changes the bacteria's genetics, where in a special case they can produce enzymes that inactivates the effects that the antibiotic has on them. If they do not get this mutation, then they can get other bacteria to transfer this mutation through a mating process, called conjugation. They can get either get it from their own type of bacteria, which is called a horizontal transfer, or they can get a transfer vertically, where they can get this genetic trait from a different type of bacteria.