Articles are words like "a", "an", and "the" that come before nouns in a sentence. Definite articles like "the" refer to specific or particular nouns, while indefinite articles like "a" and "an" refer to non-specific or non-particular nouns. Articles help identify whether the noun is referring to something specific that has already been mentioned or introduced, or something more general.

1. Definite Articles and Indefinite Articles