definite/indefinite articles

Articles
There are only three articles in the English language: a, an and the. Articles can be difficult for English learners to use correctly because many languages don’t have them (or don’t use them in the same way).
Although articles are their own part of speech, they’re technically also adjectives! Articles are used to describe which noun you’re referring to. Maybe thinking of them as adjectives will help you learn which one to use:

• A — A singular, general item.
• An — A singular, general item. Use this before words that start with a vowel.
• The — A singular or plural, specific item.

Simply put, when you’re talking about something general, use a and an. When you’re speaking about something specific, use the. “A cat” can be used to refer to any cat in the world. “The cat” is used to refer to the cat that just walked by.