A member of the violin family, the cello has four strings that are tuned in perfect fifths. It is a descendent of the viola da gamba, which looked a bit like today’s cello and was held between the knees.
Generally the cello plays in the bass clef, but not also so. It is a magnificent instrument, the sound of which can bring you to tears. If you would like to hear a cello try these links: http://www.youtube.com/watch?v=mIPq48M06Zo , http://www.youtube.com/watch?v=Rwgbczsgt3I&feature=related , and http://www.youtube.com/watch?v=ufVV1H5pkA8&feature=related .
The first link is Zara Nelsova, the magnificent cellist who introduced me to the cello in the summer of 1962 at the Aspen Music Festival. She performed Dvorak's Cello Concerto, and I will never forget the power that she got out of the instrument. All of that was well before the digital age, so there a precious few videos of her, but I did found two or three.
The second link is Yo-Yo Ma playing Tchaikovsky’s Andante Cantabile. The sound he pulls from the cello is pure velvet. Have a listen.
The third link above is Mstislav Rostropovich performing Bach’s Cello Suite #4. I include it here because he is a wonderful cellist, and I had a personal encounter with him decades ago. When I was in college at Oberlin (1963-1964) he came to the school for the weekly Convocation in Finney Chapel. I heard him play and fell in love with the cello immediately.
Three years later in Minneapolis, Rostropovich came to solo with the Minneapolis Symphony. (pre Minnesota Orchestra). The program included Stravinsky’s Symphony of Psalms, Tchaikovsky’s Rococo Variations, and something else I can no longer remember. During the work that I have forgotten, I was backstage waiting to play the Stravinsky, and he was waiting to perform the Tchaikovsky. He saw me and motioned me into his dressing room. His English was very poor then, but he had an interpreter, who came in and translated for us. I told Rostropovich that I had heard him play at Oberlin, and he reached out and held my hand while we continued to chat. I will never forget those few minutes, and as I remember, I didn’t wash that hand for at least a week.