This article on lutes is from the atlaas of plucked instruments here.
Lutes belong to the oldest plucked instruments. Lute-like instruments have been found in archeological remains in the Middle East and the Far East from as long as 4000 years ago.
In Europe lutes were the most popular instruments for a few hundred years, especially from 1400 to 1800. This can be seen from the large volume of books and manuscripts from that period.
The lute (both the instrument and the name) derives from the Arabian lute, the Ud("El Ud" - or Oud), which is still much played (see Middle East). The instrument probably reached West Europe from the Middle East via the Moors in Spain, or was brought home by the Crusadors.
Music for it was always written in tablature - a way of music notation specially for plucked stringed lute-like instruments, where not the pitch is notated, but which string on which fret has to be plucked. Several different systems were in use (Spanish, French, Italian and the most complicated: German), but all on the same basis: string + fret.
The lute era ended around 1750, when music (especially Bach's) became too complicated to be played by non-professionals on the lute, and was played more easily on keyboard instruments, like the then popular harpsichord and pianoforte.
The number of strings on a lute slowly increased from about four courses on early medieval lutes to theorbe lutes with many extra bass strings, fitted to extra long necks, reaching finally a total of 14 (double) courses, or 26 strings in total. Since the Middle Ages there were always double strings in a course.