Determiners, or noun signals, are special adjectives used before nouns.
There are different kinds of determiners.
a, an and the are called the articles.
The words this, that, these and those are also special pronouns called determiners. They are used to point out which thing or person you mean. They are called demonstrative determiners.
Words such as many, much and several tell about quantity without giving an exact number. They are called quantifying determiners.
The words what, which and whose are used before nouns to ask questions.
Interrogative determiners appear just before nouns.
The words my, your, his, her, its, our and their are used before nouns to show ownership. They are called possessive determiners.