With Factory design pattern we can create concrete products of a type that Factory can manufacture. E.g. If it is CarFactory, we can produce, Ford, Toyota, Honda, Maserati etc.
With Abstract Factory design pattern we create a concrete implementation of a Factory. E.g. DeviceFactory can be Abstract and it can give us GoogleDeviceFactory, AppleDeviceFactory etc. With AppleDeviceFactory we will get products like- iPhone, iPad, Mac etc. With GoogleDeviceFactory we will get products like- Nexus phone, Google Nexus tablet, Google ChromeBook etc.
So it is a subtle difference between Factory and Abstract Factory design pattern. One way to remember is that within Abstract Factory pattern, Factory pattern is already implemented.