Genetic engineering is the science of adding new DNA to an existing organism. This allows an organism to be given new traits that can protect or improve it in some way. Applications of genetic engineering include crop enhancement (resistance to diseases, drought, greater yield, etc.), medicinal uses, and livestock augmentations.
Humans have been breeding plants and animals to create stronger organisms since agriculture began. This new science is more effective and allows us to give organisms traits that would not be found without genetic engineering.
The science of genetic engineering is complicated and requires an understanding of DNA.