Grammar

Un, une, des: how French says a, an, and some.

If le and la mean the, un, une, and des help you introduce something new.

Un and une

Un is used with masculine nouns and une with feminine nouns.

Des means some or plural a

English has no plural form of a, but French uses des. It can mean some, or simply mark a plural noun.

Use un, une, des to introduce

Use these articles when the thing is not already known in the conversation: Je cherche un restaurant, I am looking for a restaurant.

Switch to le, la, les when specific

First mention: Je vois une boulangerie. I see a bakery. Later: La boulangerie est fermée. The bakery is closed.

This switch is small, but it makes your French sound organized and clear.