This is the King James Version (KJV) of the Bible, traditionally the principal English translation. The KJV is considered one of the masterpieces of early modern English literature, although most modern readers find the language a bit dated and occasionally opaque. There have been numerous successive English translations, many of which have borrowed heavily from the KJV.
One thing to note about the names of the books in the KJV, particularly if you are linking to the files here: the KJV books called 1, 2, 3 and 4 Kings are called Samuel 1 and 2, and Kings 1 and 2 respectively in other versions and translations. However, the abbreviations used at this site are sa1, sa2, ki1 and ki2 respectively across all of the Bible etexts.