They are computer software thingies so yes and no. When they perform, they are projected on to a screen (holograms). No, they are not real, actual living people.
Yes. There are a lot already.
A otaku is someone who has no life and spends there time watching anime and is probally addicted [like me :D] so a vocaloid otoku is some one watches vocaloid to much and has no social life [I know tr;dl]
Ramune-P.
Hatsune Miku is a representation of Yamaha's Vocaloid computer program.
No. She is just a fanmade Vocal with Miku and Rin's voice.
Yes, Ai is a vocaloid. A vocaloid 3 to be exact.
No. But they were voice provided by real people such as Miriam Stockley, Saki Fujita, YOHIO, MiKA, and more
No one. She is just a man-made singing program, not a real being.
Vocaloid fans like Vocaloid. Vocaloid fans are located around the world. Vocaloid fans also have a tendency to like Japanese animation (anime) and comics (manga).
Piko is the name of both the Vocaloid and the voice provider, who is naturally not a Vocaloid.
Teto Kasane is both somewhat a Vocaloid and a UTAUloid. Utau is like Vocaloid only thing is you can make your own voice into a UTAUloid and its free. But it is very hard to use. If you go on www.youtube.com or www.nicovideo.jp you will probably see alot of UTAUloids and fanmade ones. The big difference of Vocaloids and UTAUloids are UTAUloids sound not as good as Vocaloids. But both have MMD Models. She is a Vocaloid character, but she is also part of the UTAUloids.
No Teto is not a Vocaloid. I have heard before that She was made to be a prank. She is mistaken to be a Vocaloid. She sounds like a Vocaloid(y) software.