If you haven't at least heard of Pink Floyd, I pity you and your poor, secluded soul. Pink Floyd is one of, if not the most famous rock band produced by Great Britain.
Pink Floyd originally started in aninomity, as most bands do. They formed in 1966. The original band consisted of vocalist and guitarist Syd Barret, drummer Nick Mason, keyboardist Rick Wright, and most importantly, bassist Roger Waters. At first, the band created a slight stir with several small releases. It had its group of fans, but they did not make a formidable amount. Their first album was The Piper at the Gates of Dawn. It is an album consisting of whimsical, bizarre songs, and it fit the time period perfectly. While Sid Barret was vocalist, they made some psychedelic works such as Apples and Oranges. However, Syd Barret was quite fond of a drug known as acid, and he had to leave the band in early '68. He was an eccentric and was mentally unstable. After releasing two more solo albums, Syd Barret slowly went insane and died after living a long life as a recluse. Anyways, back to Floyd. David Gilmour then joined the band to replace Syd. In '68, Floyd made another interesting album called A Saucerful of Secrets. This album features the instrumental, "out-of-this-world", hypnotic and psychedelic piece called "Set the Controls for the Heart of the Sun". After that, Pink Floyd made several more albums mentioned in the wonderful discography above. The next album that was particularly noticeable in their history is Atom Heart Mother, which was their first one to hit No. 1 on the charts in 1970. The next album, Meddle, featured a song called Echoes (a personal favorite) which is a groundbreaking 21 minutes long. Echoes is a song which mixes mysterious and thought-provoking lyrics with an excellent musical accompaniment, with the sounds of "wind" occasionally thrown in (go figure, it's Pink Floyd we're talking about). After that, they performed in a series of concerts, and released a little-known album called Obscured by Clouds. Obscured by Clouds was basically the predecessor to Dark Side of the Moon. To be brutally and historically accurate, Obscured was more or less Floyd's last-ditch effort to stay together as a band. At that point, they were pseudo-succesfull as a band, and it is generally a well-known fact that they didn't have enough energy and money to keep going. Unless, that is, they got some kind of break.
This break came in the form of a very well-known album (this is a gross understatement) called The Dark Side of the Moon. Dark Side is an extremely famous album, and it was on the top for over 625 weeks. That's over 13 years, for those who are too lazy or inept to do the calculations. There are even some interesting stories (myths?) about this album, such as The Dark Side of the Rainbow. This album earned them a hell of a lot of money, proper recognition, and a very formidable fan base. After that, their history is fairly well-known, so I won't bother getting into too much detail. They made the album Animals, which is actually a parallel to George Orwell's book, Animal Farm. They also created The Wall, which along with Dark Side is their most famous album and was later made into The Wall DVD. Thanks to Roger Waters, The Wall was also made into a very succesfull live show, which Floyd performed countless times in many interesting places. Another noticeable release was Wish You Were Here, a popular favorite and ranking alongside with Animals and The Wall. By the end of the 70s, Pink Floyd was one of the most well-known and greatest bands in the world. Unfortunately everything went downhill from there. In the 80s and 90s their albums didn't meet with such success, and they eventually broke up. They did get together and create the Division Bell, but it's not nearly as remarkable as their early works.
Their musical style is hard to describe, especially keeping in mind it's different variations over time. Therfore, I will provide a more chronological description. In the 60s, while they still had Sid Barret, the sound was very "psychedelic". Think Traffic, Or Jefferson Airplane. They had some very strange sound effects mixed in, and the vocals sounded somewhat detached and off in another world (or dimension). After that, they started creating a more practical sound, while retaining a unique quality. Dark Side was a turning point for Floyd, and out of all the albums it has easily the most diverse and unique sound. It features the saxophone, very impressive female vocals, and a great combination of keyboard, guitar, and bass. The albums after that have some kind of discernible pattern. This consists of a rhythm created with the guitar and drums (or bass, if regarding The Wall), topped with Roger Waters' vocals. However, it would be foolhardy and nearly impossible to generalize Pink Floyd's sound. As a general rule, it's obviously best to actually listen to music to really understand what is sounds like.