These are the main determiners. There can be only ONE main determiner in a noun phrase (for more about this, see order of determiners):

1. Articles - The determiners a/an and the are called "articles". They are the most common of all determiners. They come at the very beginning of a noun phrase

2. Demonstrative Determiners - The demonstrative determiners this/that, these/those point to something that is close or distant.

3. Possessive Determiners - We use possessive determiners ( my, your, his, her, its, our, their ) to show who owns or "possesses" something.