In German just like in English we have determiners. Determiners help point specifically to what is being talked about.

e.g. A man is talking — the determiner here is 'A' indicating an indefinite, nonspecific man.

e.g. The people are talking — 'The' is pointing to a specific group of people.

Below are all the different types of determiners in English. It's important that you refamiliarise yourself with them before moving onto learning German.