You can use the incubator you have to hatch them into other Pok?mon characters. By leveling up you will also get more incubators or can buy some in the store. Each egg requires you to walk a certain distance before it hatches in the incubator.
The eggs allow you to hatch pokemon. The way to do it, is to select an egg, put it in an incubator, and then walk the necessary kilometers while the app is open and it will hatch the egg and you will have a pokemon. Enjoy