Anbu Purpose

ANBU are under direct control of their Kage. They protect the village from exceptional threats, conduct high risk missions into enemy countries, and deal with extremely strong ninja. They are also responsible for carrying out assassinations, tracking, surveillance and missions requiring specially trained ninja. Some ANBU serve as interrogators that probe the minds of enemy ninja to learn information valuable to the village. If an ANBU dies during a mission they are required to destroy their bodies.

In Konohagakure there exists a special branch of the ANBU known as the Foundation "root" in the original manga and here). The Foundation was created and led by Danzo, who sends its members on missions that he believes will benefit Konoha. Foundation members are trained to abandon all forms of emotion to follow Danzo's orders unquestioningly.

ANBU have a detailed knowledge of the human body and can use such jutsu as Temporary Paralysis Technique and Time Reversal Technique to take advantage of this