Todos os verbos e auxiliares aqui são usados no presente simples.

A forma verbal are é usado com os pronomes pessoais you, we e they; aren't é a forma negativa. A forma verbal is é usado com os pronomes pessoais he, she e it; isn't é a forma negativa.

Ex.: You are a happy person. - You aren't a happy person.

They are worried about the accident. - They aren't worried about the accident.

He is proud of his accomplishments. - He isn't proud of his accomplishments.

O auxiliar do é usado com os pronomes pessoais I, you, we e they; don't é a forma negativa. O auxiliar does é usado com os pronomes pessoais he, she e it; doesn't é a forma negativa. Você precisa um desses auxiliares para fazer a interrogativa ou negativa quando o verbo não for o to be.

Ex.: Do I know her? - I don't know her.

Does she like her family? - She doesn't like her family.

Do they cry themselves to sleep every night? - They don't cry themselves to sleep every night.

Para dar respostas curtas, você também usa esses verbos.

Ex.: Do you like going to the club? Yes, I do ou No, I don't.

Are they getting married next year? Yes, they are ou No, they aren't.

Is the dog barking right now? Yes, it is ou No, it isn't.