Articles are words like "the", "a", and "an" that are used before nouns. There are three choices for articles: "the" for specific or definite nouns, "a" or "an" for general or indefinite singular nouns, and nothing for plural or uncountable nouns. To choose the correct article, you must consider whether the noun is definite or indefinite, countable or uncountable, and singular or plural. The definite article "the" is used when the noun is unique or specifically referred to based on context. The indefinite articles "a" or "an" are used when the noun is nonspecific or generalized.