What Are Articles?
The articles in English are the (definite article), a, and an (indefinite articles).
Articles define a noun as specific or unspecific.
After the long day, the cup of tea tastes particularly good.
By using the, we’ve shown that it was one specific day that was long, and one specific cup of tea that tasted good.
After a long day, a cup of tea tastes particularly good.
By using a, we’ve created a general statement, saying that any cup of tea would taste good after any long day.