Learn French: Ces étudiants viennent d'où ? - Where do these students come from?

Où means "where", but when asking where someone comes from, French uses de (from) + où (where). Because où starts with a vowel, de drops its "e" and becomes d', making d'où.

Why is the question word d'où at the very end of the sentence?

In everyday, spoken French, it is very common to keep the normal subject-verb order (Ces étudiants viennent) and just add the question word at the end. A more formal way to ask this would be putting the question word first: D'où viennent ces étudiants ?

How do I pronounce the verb viennent? Do I say the "-ent" at the end?

No, the -ent ending on verbs for "they" (like viennent) is completely silent in French! You just pronounce the base part of the word, which sounds like "vyenn".

What does ces mean here, and how is it pronounced with étudiants?

Ces is a plural word meaning "these" or "those". Because étudiants starts with a vowel sound, the normally silent "s" at the end of ces wakes up and makes a "z" sound to link the two words together. This linking is called a liaison.