Web sites are very dull with just words, no matter what you have to say.
Images bring a site to life.
In simple terms, we're talking pictures. But in computer terms, we're talking about data, bytes, etc. These pixels are like tiny dots that are so small you can't see them. Maybe you've seen a painting made like this. Up close, you could tell that the artist painted the picture using little dabs of paint to make dots, but away from the painting the dots came together to form an image of the whole painting.