Satellite Navigation systems is a device that allows you to enter an address of place of interest and it will plot the route for you. You can then follow the on screen directions to arrive at your destination.
Sat nav’s vary greatly dependent on model and often price. Many car manufactures offer a factory fitted sat nav that is built in to the car from new or you can buy an aftermarket one. Some of the better models offer traffic reporting and automatic re-routing along with speed camera detection and speed monitoring.
Prices range from as little as £50 up in to the high hundreds but you often do get what you pay for. It is worth investing it a higher spec model if possible as poorer models can have issues with receiving GPS signal and re-routing should you need to divert.
Most sat navs require updates to allow the mapping system to include / exclude roads that have been changed (such as islands added or made one way).