Its focus is not on the procedures of the modeled world, but on the objects appearing in it.
Objects are natural things to model because that's what the world is made of.
Planes, dogs, and computers are all objects. Even abstract concepts, such as a priority queue, can be thought of as an object. What all objects have in common is that they have state and behavior. For example, the state of a plane can be partially indicated by its speed and location, but its behavior might be represented by its ability to change altitude. When modeling a car engine, for example, you can focus on the characteristics of each object in the engine as opposed to the flow of gas and energy through it.