This article is from the World English Bible Translation FAQ, by Michael Paul Johnson firstname.lastname@example.org with numerous contributions by others.
"Yahweh" is the most probable best transliteration of this most holy
proper name from the Hebrew consonants YOD HE WAW HE, or YHWH. This holy
name is sometimes rendered "Jehovah" based on the mixture of the vowels
for "Adonai" (Lord) with the consonants "YHWH" as it is written in some
later Hebrew manuscripts. The original Hebrew manuscripts had no vowels,
and we believe that the vowels for "adonai" were added to reflect the
tradition of avoiding pronouncing God's name, and saying "Lord" instead,
and was not an indication of how the name should be pronounced by those
so bold as to actually utter God's name. This is a break from the
tradition of the KJV and others that use "LORD" or "GOD" with all caps
or small caps to translate "YHWH", and use "Lord" (normal mixed case) to
translate "Adonai" and "God" (normal mixed case) to translate "Elohim."
That tradition gets really confusing in some places, especially since
"Yahweh" is used in conjunction with "Lord" and "God" in many places in
the Old Testament. Since God's proper name really is separate from the
titles "Lord" and "God" in the original Hebrew, we wanted the English
translation to reflect that fact, even when read aloud.
In some places, "Yah," a shortened version of God's Name is used. This
is how it is written in the Hebrew manuscripts in those places. As a
concession to strong tradition, the Hebrew Names Version of the World
English Bible uses "LORD" or "GOD" (all capital letters) for "Yahweh."