ANBU stands for Ansatsu Senjutsu Tokushu Butai or Assassination Tactics Special Squad.
this elite squad worked under direct order from the Hokage. the true identity of the members is a top secret. their distinctive features are the uniform, a tattoo on their left arm, and a mask (omen) they always wear on duty. in Japan, you can find and buy these masks in Japanese festivals (esp. during summer). the figures are mostly animals such as dog, cat, fox, bird, etc. some members also wear black coat.
Age : ?
Yamato is assigned by Tsunade to replace Kakashi's position as leader of the new Team 7 because he is the best ANBU member. the fact is that Yamato was one and only survivor of Orochimaru's mutation experiment of Shodaime's gen. thus he inherited the skills of Shodaime such as wood element (mokuton) mastery and a very rare ability to control Jinchuuriki. Yamato seems to be good at intimidating people (esp. Naruto ^o^) He, Naruto, Sakura and Sai are leading a mission to find Orochimaru and Sasuke. indeed Yamato is a code name, his real name is Tenzou.
Age : 29 (Sep 15)
Rank : Jounin
the most popular jounin in Konoha. he is known as a genius and a copycat. the implant sharingan in his left eye enables him to copy his opponent's jutsu. passed the chuunin exam when he was only 6, then joined with the ANBU. yet he have a terrible habit i.e. always comes late with irrational reasons. not to mention, his hobby reading adult novels "Icha Icha Tactics". he's the one who invented a lethal jutsu, Chidori/Raikiri, which he later taught to Sasuke. Kakashi has ill memories of losing his beloved people. his father, Hatake "White Fang" Sakumo, committed suicide after being humiliated by his own comrades for trespassing the law. when Kakashi was a kid, he has 2 teammates i.e. Uchiha Obito and Rin. Kakashi's sharingan is indeed a memento from Obito who died on Kakashi's first jounin assignment.
Age : 20 (Jun 9)
Organization : Akatsuki
Ring : Shu (scarlet) taken from Suzaku (red phoenix)
Ring position : Right ring finger
the big brother of Sasuke and the man who slaughtered his own clan in just one night. thus he's listed in Bingo book. has incredible records i.e. graduated from ninja academy at age 7, awakened the sharingan at age 8, passed chuunin exam at age 10, and led the ANBU at age 13. however, he hates his fate as Uchiha successor and decided to do his own way. secretly he killed his own best pal, Uchiha Shisui, to obtain the mangekyou. yet he let his lil bro alive, thus Sasuke will hate him, curse him, and kill him one day. once he returned to Konoha with his new comrade, Kisame, to abduct Naruto. thank God, Jiraiya came at the nick of the time and halted their mission.
Root is a separated training division of ANBU, yet it has been disbanded. in Root you have no name, no feelings, no past, no future, all that exist is the mission. the unseen ones who support the great tree of Konoha from the depths of the earth.
Age : 15
Sai was assigned to join with Naruto team, as Sasuke's subtitue, but on the other hand he was ordered by Danzo to join forces as well as spy on Orochimaru. his unique ninjutsu is called Choujuu Giga i.e. a jutsu to animate ink drawings. Sai seems to have ill memories of his past, related with his late big brother. Sai may have a smiley face but he loves talking in insensitive and vulgar language which often makes Naruto becomes sulky ^^".
Rank : Rokudaime Hokage
Age : ? (deceased)
this bandaged man is known as an elder who opposed of late Sandaime in his past. behind his bandage on his right arm and eye is full of Sharingans. his right eye is from Shisui's (this enable him to manipulate other people's thoughts without them being aware of it) and his right hand also full with Sharingan eyes (this enable him to use Izanagi, a forbidden jutsu that able to control space between reality and illusion). he competed for the chair of Sandaime Hokage. an overly serious, militaristic logical thinking ex-leader of "Root" and Sai's superior. he sent Sai as a messenger to join forces with Orochimaru and destroy Konoha. however, Yamato busted Sai at Orochimaru's lair before the plan works and Sai decided to back up Naruto instead. Danzo took the position of the 6th Hokage when Tsunade went into unconscious condition after Akatsuki invasion on Konoha led by Pain. Danzo comes to the Kage Summit on Iron Country as Hokage, but Sasuke also arrived at the meeting to take revenge and finally able to kill Danzo.