Hens will lay eggs with or without the presence of a Rooster. The rooster will insure that the eggs are fertilized and if you would have a broody hen or an incubator you would be able to have those eggs hatched to chicks. Without the rooster it would not be possible.
Do Fertilized eggs look or taste differently? It's an understandable question to have, with various opinions. The truth is, that if you collect your eggs in a good amount of time, it takes a very trained eye to see if the eggs are fertilized. An unfertilized egg has a small white spot on the yolk, and when an egg is fertilized that small white dot looks like it has a new center (like a bull's eye). There is no taste difference and no difference in looks other than the small white spot that becomes a small bull's eye.
There are a lot of misconceptions about fertilized eggs vs. unfertilized eggs, to find out information on this and more reference our Everything Eggs Article.