One of the most common confusions that students end up having is differentiating between GPS and GIS. Simply put, the Global Positioning System (GPS) is a U.S. based satellite system used to find the exact location of something on Earth's surface. It uses satellites in orbit around the planet, each of which is controlled from tracking stations that monitor the satellites and control them when necessary. Those satellites send information down to recievers on the ground. When you are holding a GPS reciever (or smartphone, or other GPS compatible device) you are recieving signals from those satellites. It takes 4 satellites to pinpoint your location. Here are a couple videos talking about the U.S. GPS system and how it is used.

Geographic Information Systems (GIS), on the other hand, IS NOT a satellite system. Instead, GIS are databases that contain multitudes of geographic data that can be layered on top of one another to make a more comprehensive map. For example, within a GIS database that has maps of Phoenix, AZ you might find maps that show roads, maps that show underground water resources, maps that show surveyed minerals, maps that show restaurants, etc. GIS can compile these maps together (a process known as a mashup) to create a more useful comprehensive map that provides lots of information. You can also go to a college or trade school to learn how to use GIS, which is a growing field in our data-driven economy. Simply put, geographers use GIS to map out data over an area. Here is a video that helps tell you how GIS works.