Justin Sandercoe has thought long and hard about how to teach people to play the guitar, and how to do this over the internet. He has come up with a well-designed series of courses that will take you from nowhere to proficiency. I tried to learn how to play years ago, using books, and got nowhere. I've been using Justin's site for just over a year and I feel I've made real progress. What's more, Justin offers his lessons for free - a boon for any young player who has the urge to play, but whose pockets are empty. I've seen and used other sites for learners: none of them offer as clearly marked a road as Justin does.
The Spanish vihuela, called in Italian the "viola da mano", a guitar-like instrument of the 15th and 16th centuries, is widely considered to have been the single most important influence in the development of the baroque guitar. It had six courses (usually), lute-like tuning in fourths and a guitar-like body, although early representations reveal an instrument with a sharply cut waist. It was also larger than the contemporary four-course guitars. By the 16th century, the vihuela's construction had more in common with the modern guitar, with its curved one-piece ribs, than with the viols, and more like a larger version of the contemporary four-course guitars. The vihuela enjoyed only a relatively short period of popularity in Spain and Italy during an era dominated elsewhere in Europe by the lute; the last surviving published music for the instrument appeared in 1576.
Guitars have been played since the Renaissance era, after descending from the ancient Greek instrument, the kithara. Or, at least, that's how the theory goes: the only real proof for this is the similarities between the Greek word and the Spanish word, quitarra. Early guitars often had four strings, evolving into the six-string version we know today in the late 1600s. Anton Stradivari, the famous violin-maker, also had a hand in making guitars. There's now only one Stradivarius guitar left in existence.