Entities

Everything you can display in AndEngine is an entity. The Entity class is a basic class that stands on top of the hierarchy. The Entity class has all the parameters the displayable objects need, such as position, scale factor, color, and so on. But on its own, it doesn't display anything.

The Entity class can also have children, both in Java class hierarchy and in the hierarchy of AndEngine objects.

For the former case, let's take the Sprite class as an example. A sprite in AndEngine is a simple image rendered on a quad (a square made of two triangles). The Sprite class extends the Shape class, which already knows what to do when the programmer sets its height and width; therefore, the Sprite class doesn't need to implement it. Also, the Shape class extends the Entity class. See the following diagram for another example:

The latter case means that you can attach one entity to another. It doesn't matter what type it is, whether it's a sprite, shape, or anything...