An object is a specific instance of a class - think of the class as a blueprint and the object as the actual house built from that blueprint. When you write Car myCar;, you create an object named myCar from the Car class.
Each object has its own copy of member variables. If you create Car car1; and Car car2;, changing car1.speed doesn't affect car2.speed. They're independent entities sharing the same structure and behavior defined in the class.
Objects live in memory with real values. The class just describes what those values should be. You can create unlimited objects from one class, each maintaining its own state.