Map tiles are the little square images which our web maps assemble into useful interactive maps. OpenStreet map describes tiles like this. In essence they are commonly used to serve up imagery or pre-rendered cartographic datasets inside a web mapping environment. Map tiles are also a very useful alternative to using vector data, when the amount of data becomes too dense. Map tiles are a base technology of modern web maps.
What do people actually do on your map?
It is likely you have a pretty solid idea of what you would like your users to be doing on your map. It is likely you want those users to investigate the subject matter layers you are presenting and marvel at the new information they have discovered from your work of cartographic web excellence.