In Naruto, there are 9 demons known as Bijuus. Bijuus are beasts of immense power, practically over-flowing with Chakra. Each Bijuu is identified by its number of tails. So far we have seen 3 Bijuus: Kyuubi, the 9-tailed fox, Shukaku, the 1-tailed raccoon-dog, and most recently, Nibi, the 2-tailed cat. The Jinchuuriki are the hosts of these beasts. Jinchuuriki are needed because the only way to defeat the Bijuu is to seal them within a newborn baby.
The three-tailed beast is a gigantic, turtle-like demon. The abilities of this creature, at the moment, are unknown. Sanbi is extremely large and also has great speed. What makes the Sanbi unique from the other demons, is that it does not have a host and it doesn't seem to have any sign of intelligence. According to Deidara of Akatsuki, not having a host makes it weaker because it isn't intelligent enough to control its own strength. Other than the fact that this demon has four tails, nothing much else is known, not even what animal it is. The host of this demon was an elderly man. He can be recognized by dark marks under his eyes, most likely from the demon. This man uses many elemental fusion techniques when battling, which could be some of the powers from the demon. This 4-tailed creature was captured by the Akatsuki after Kisame killed its host
Gobi no Houkou, takes the form of a dog in Japanese mythology. This demon has not featured in the Naruto series as of yet
Kyuubi is the 9-tailed fox sealed within Naruto. This Bijuu attacked the village of Konoha 12 years nearly destroying the village and all its inhabitants. The 4th Hokage sacrificed himself, using a technique known only to him and the 3rd Hokage, and sealed Kyuubi in an infant named: Naruto. Because of the Kyuubi, the villagers ignored Naruto and viewed him as a nuisance leaving him sad and alone. The power of the Kyuubi is so great that when Naruto is cut or wounded Chakra leaks from the wound and heals it almost instantly. Naruto is able tap into Kyuubi's power by begging it to let him borrow Chakra. When Naruto becomes enraged the Kyuubi takes over his body and forms a Kyuubi-shaped shell of red Chakra around Naruto