Learn Dutch: Mijn moeder is blij, want de keuken is schoon. - My mother is happy, because the kitchen is clean.

Want is a coordinating conjunction, which is just a grammar term meaning it connects two independent sentences without changing them. It acts just like en (and) or maar (but). The word order in the second part stays exactly the same as a normal, standalone sentence: Subject (de keuken) + Verb (is) + Adjective (schoon).

I thought the Dutch word for "because" was omdat. Can I use omdat here instead?

You could, but it would change the word order! Both want and omdat translate to "because". However, want keeps the normal word order, while omdat pushes the verb to the very end of the sentence (... omdat de keuken schoon is). For beginners, want is often easier to use because you don't have to rearrange the words!

Does schoon mean "clean" or "beautiful"?

In standard Dutch, schoon means "clean". If you know some German, be careful: it looks a lot like the German word "schön" (beautiful), but they are false friends! If you want to say "beautiful" in Dutch, you use mooi. (Note: In the Flanders region of Belgium, you might still hear schoon used to mean "beautiful").

Is the comma before want required?