What Text Are the Translators Translating?

What is it that Bible translators translate when they are translating?  Let me focus on the New Testament, my main area of expertise.   When a translator wants to make an English version of, say, Mark (what I say about Mark will be true of all the books of the NT), what does she actually translate into English? Obviously she cannot take Mark’s original manuscript and translate it, since we don’t have it.  Or the first copy of the original, or a copy of the copy of the original.   We have hundreds of copies of Mark.  Does she just choose one that seems good and translate that? No, as it turns out, that’s not how it works at all.  She translates a critical edition of the Greek text of Mark as it has been reconstructed by textual scholars.  This will take a good bit of explaining. From near the time in the fifteenth century when printing with moveable type was invented there have been scholars interested in producing printed versions of the Greek New Testament (and [...]