What is a mashup?

A mashup is basically a website or application that integrates information of two or more other websites. At the moment many mashups are a combination of GoogleMaps and one or two other websites, which allow you to search for a location of something on a map. Other mashups allow you to compare prices of products from other websites, but many other combinations are possible. At the moment many creative volunteer programmers are making all kinds of mashups and are constantly trying to find new combinations.