Abstract Factory pattern is another creational design pattern in the league of Factory, Singleton, builder and Prototype patterns. The term has some resemblance to Factory pattern and so does implementation. I tried looking around the internet to figure out some good explanation, but unfortunately they are too complex. This will help though- http://www.oodesign.com/abstract-factory-pattern.html
In my attempt to over simply things, I will try to go back to factory pattern and the example I used for CarFactory, http://kamalmeet.com/2013/06/factory-pattern/. The idea was simple with CarFactory, that user knows he wants a car, but which car is to be created is decided at runtime.
AbstractFactory Extends the idea a bit further, it gives us a factory of factories.
To understand the above diagram, lets extend our CarFactory example, lets say we know that we need a vehicle to start with but we do not know if it will be a car or a bike (decided at runtime). So we will have 2 concrete factories- CarFactory and BikeFactory. CarFactory is responsible for creating Sedan or HatchBack as previous example and BikeFactory is creating SportsBike and NormalBike. On top of the concrete factories we will introduce a AbstractVehicalFactory which is implemented by CarFactory and BikeFactory.