Known in the 18th century simply as Flute = Flauto - the transverse form was separately referred to as Traverso. It was for the recorder that J.S. Bach wrote the 4th Brandenburg concerto in G major (though Thurston Dart[?] controversially suggested that it was intended for flageolets at a higher pitch, and in a recording under Neville Marriner[?] using Dart's editions it was played an octave higher than usual on sopranino recorders).
The instrument went into decline after the 18th century, being used for about the last time as an other-wordly sound by Gluck in his opera Orfeo ed Euridice[?]. Although it was revived at the end of the 19th century by the English researcher into Early Music, Arnold Dolmetsch[?], even in the early 20th century it was uncommon enough that Stravinsky thought it to be a kind of clarinet when first seeing one. Subsequent to its rediscovery it became very popular in schools, since it is inexpensive, easy to play at some level, is pre-tuned (and thus even the tone-deaf can play in tune with the rest of an ensemble), and is not too strident in even the most musically-inept hands. It is however incorrect to assume that mastery is similarly easy - like other instruments, it requires talent and study to play it at an advanced level.
Recorders come in two kinds: tuned in C and in F. The normal, school instrument, recorder is the soprano in C, which has a lowest note of c'. Above this are the sopranino in F and the "gar klein floetlein" in C. Below the soprano are the alto in F, tenor in C and bass in F. Lower instruments in C and F exist, but are more rare. They are also difficult to handle: the sub bass in F is about 2 meters tall. The soprano and the alto are the most common solo instruments in the recorder family.
The range of a recorder is more or less 2 octaves, chromatically. Some higher notes exist, but notably the augmented prime, two octaves above the base note, is absent. Basically, a recorder is a diatonic instrument, with one hole for each note of the scale of its lowest note. The chromatic scale degrees are played by so-called "fork" fingerings, uncovering one hole and covering one or more of the ones below it. Fork fingerings have a different tonal character from the diatonic notes, giving the recorder its characteristic, woody, and somewhat uneven sound.
See also: recorder player