What is the difference between factory and abstract factory pattern?

The Factory pattern is applicable for a single class whereas AbstractFactory is for a set of classes. AbstractFactory uses the Factory pattern for each class in addition to defining a few other things.

With the Factory pattern, you produce implementations (Apple, Banana, Cherry, etc.) of a particular interface -- say, IFruit.

With the Abstract Factory pattern, you produce implementations of a particular Factory interface -- e.g.,IFruitFactory. Each of those knows how to create different kinds of fruit.