Learn French: Le jeudi, ils mangent au restaurant. - On Thursdays, they eat at the restaurant.

In French, to express a recurring habit on a specific day, you use the singular article le before the day. So le jeudi literally means "the Thursday" but translates to "every Thursday" or "on Thursdays".

Why isn't jeudi capitalized here?

Unlike English, French does not capitalize days of the week or months unless they appear at the very beginning of a sentence.

How is the verb mangent pronounced? Do I say the "-ent" at the end?

No, the -ent ending on French verbs used with ils or elles (they) is always completely silent. You pronounce mangent exactly the same way as the singular form mange.

Why does the sentence use au restaurant instead of à le restaurant?

In French, whenever the preposition à (at/to) meets the masculine article le (the), they must contract into the single word au. Since restaurant is a masculine noun, à + le becomes au.