Evolution is the process of change that enables life to adapt to its surroundings.
When animals and some plants reproduce, each parent contributes half of the offspring’s genetic information. The genes that are passed on to offspring are similar to, but never exactly the same as, the parent genes.
While we are alive, our bodies can adapt to certain elements in our environment. For instance, an immunity to a disease can be developed and possibly passed on genetically to our offspring.
The offspring would not have to develop that immunity, they would inherit it. In this way, the variety of possible life grows, from single cells to dinosaurs and humans.