Geocoding addresses in Salesforce gives you the ability to do neat things like show which Accounts or Contacts are near to each other, or near to your current location.

It is the process of taking an address and turning it into longitude/latitude coordinates. For a long time the way to do this way via the Google Maps API. Unfortunately, that means writing an integration to the Maps API, and making sure that you don't use it too heavily and end up reaching the level where you have to pay Google for the use. 

You can now do this by just setting up Data.com Clean Rules (not extra licensing required). This is outstandingly useful functionality to get with no code and no extra cost!