The prefix "bio-" refers to natural living organisms. Biotechnology is the practice of using and adapting living creatures to serve the needs of humans.
Even the domestication of farm animals (instead of hunting), or the act of planting seeds (instead of foraging for plants) could be considered to be very basic forms of biotechnology. As science and industry progressed, humans learned how to breed plants and animals to emphasize certain traits, such as longevity, taste, and yield.
Today, biotechnology includes modification of living creatures at the genetic level. Instead of choosing parents and hoping their offspring are what we’re looking for, we can just alter specific genes to ensure that the animals and plants develop specific traits for food, medicine, and other human needs.
There is a lot of controversy today about GMOs (Genetically Modified Organisms). It is important to regulate this practice because genetic modification can have positive and negative results, both on the natural world when the creatures are taken out of the lab, and on the people and animals who consume food made from GMOs.