the

We use the to refer to a specific something. So we use the only when everyone knows what you refer to. When there is only one thing you could mean.

 

The man was following me.

I grabbed the chair.

I walked past the school.

He grabbed the laptop.

 

We usually use the when something is referred to for the second time.

For example:

- An apple fell off the tree. He grabbed the apple and ate it.

- A dog was barking. I told the dog to shut up.

- Oh my gosh! A child got hit by a car! The car was driving too fast.