Think of a sentence like a little team. The simple subject is the star player—the person, place, or thing doing the action or being talked about. It’s not the whole fancy description; it’s the core.
For example, in “The fluffy, sleepy cat yawned,” who is the star? It’s the cat. Not “the fluffy, sleepy cat,” but just cat. Simple, right?
Why does this matter? Because once you find that one word, the whole sentence suddenly makes perfect sense. It’s like finding the remote control when you thought you’d lost it forever.