Learn French: Est-ce que vous préférez ce pain ?

Ce is the demonstrative adjective for "this" or "that" used with masculine singular nouns that start with a consonant. Since pain (bread) is masculine and starts with a consonant, we use ce. You would use cette if the word was feminine, and cet if it was masculine but started with a vowel or silent H.

Can ce pain mean "that bread" as well as "this bread"?

Yes! French words like ce do not distinguish between "this" and "that" on their own. The context usually makes it clear. If you really need to specify, you can add -ci to the noun for "this" (ce pain-ci) or -là for "that" (ce pain-là).

How does Est-ce que work in this sentence?

Est-ce que is a very common phrase used to turn a regular statement into a yes/no question. If you take the statement vous préférez ce pain (you prefer this bread) and simply put Est-ce que in front of it, it becomes "Do you prefer this bread?".

I've seen the verb written as préfère before. Why is it préférez here?