Mashup

From DaveWiki

A mashup is an application or service that takes information from one source, and combines it with information from another, creating extra value for the user.

One of those information sources is often a map, so information is plotted on a map to provide context, though this does not have to always be the case.

Government sites such as http://www.data.gov.uk provide data sets for hackers to use to create mashups.