Some of my students really struggle with the three small words: «a», «an» and «the». So I decided to look at them a little closer, as this is something that really comes naturally for English speakers (although some do get the use of «a» and «an» wrong!)
An article is actually an adjective (wow! this makes no sense) but if you think carefully, we always use them before a person, place, object or idea. These are all nouns, so, an article is an adjective... We use articles to point out, or refer to nouns.
Now, divide them into two groups: definite and indefinite articles.
A definite article is very specific and direct: the earth, the food on my plate, the car I am driving. It always refers directly to a noun (or a group of nouns) and for this we use «the».
Now, indefinite articles are not specific: I ate an apple, there is a car in the street, the man saw a dog. We are no longer talking about one specific noun, but are referring to a noun from a group of nouns — it was just a dog, not a specific one.
Be careful, when the noun starts with a vowel (or a vowel sound!) we use «an»: an Eskimo but a cat.
Much more can be said about these three tiny, annoying little words but the only thing I want to say more is: do not use them too often! It is the one common error made by non-native speakers, especially if your native language doesn’t use them. Please say: «I traveled to Moscow» and not «I traveled to the Moscow»!
Happy reading and happy speaking, till next time!