"The" is known as a definite article and it belongs to the English word class called determiners.

The most common determiners in English include a, an, the, and some.

"The" is used before a noun to show that the identity of the thing being referred to is known to the reader, or to both the speaker and the listener.

https://www.youtube.com/watch?v=I3n_X9mKjmI

To most people, this is probably the only way to use this common English function word.

Click below for details on 12 different ways to use "the" in English speech and writing.