Meaning: This sentence means that the specific cat being referred to is currently moving quickly on foot with long, rapid steps.
Choice of Words: The word "The" is used to refer to a specific cat. "Cat" is a noun that refers to a small, domesticated carnivorous mammal with soft fur, a long tail, and sharp claws. "Is" is a form of the verb "to be", which is used to describe an ongoing action. "Running" means moving quickly on foot with long, rapid steps.