SEELE is a shadowy and mysterious organization which maintains a global power cabal, and is the secret backer of GEHIRN and NERV. The SEELE council members are the true puppetmasters pulling the strings of the United Nations.
The origins of SEELE are shrouded in mystery. According to themselves, they have maintained an Illuminati-like power cabal over Earth's governments since ancient times. While this can not be independently confirmed, it is certain that SEELE has been active since at least the end of World War II, when they acquired the Dead Sea Scrolls.
The SEELE council is composed of 12 members, headed by Chairman Keel Lorenz. SEELE meetings consist of "videoconferences" in which instead of projecting actual images of each member, images of large stone monoliths with the words "SEELE (member number) SOUND ONLY" displayed on them (i.e. Chairman Keel is "SEELE 01 SOUND ONLY").
Apparently the inner circle of SEELE is the Instrumentality Committee, which directly oversees the progress of NERV, officially in the name of the United Nations (which it actually controls). The Instrumentality Committee is composed of five members, and is also headed by Chairman Keel.