Although there are many ways in which geographers use technology today, perhaps the most important technology for geographers is Geographic Information Systems (GIS). This is a term for computerized mapping and informational systems that are used for a variety of purposes. The major change over the years has been a change from information being kept on paper to information being stored on computers in ways that can be used by the GIS.
In times past, geographers would often use paper or plastic maps. They might have an underlying map of an area and then have plastic overlays that they could put over the maps. For example, an overlay might give rainfall data for various areas or it might show isotherms, which are lines that connect places with similar temperatures.
Today, GIS has done away with the need for the physical maps and overlays. GIS can use the power of computers to put an array of data over the basic map of an area. For example, it might show economic data along with ethnic/demographic data on a map of a given area. Essentially, anything that can be mapped by a geographer can be put on GIS so that it can be searchable and more easily used than the old style physical maps were.