Scottish Rite of Freemasonry on Wikipedia
The Ancient and Accepted Scottish Rite of Freemasonry, commonly known as simply the Scottish Rite, is one of several Rites of Freemasonry.
A Rite is a progressive series of degrees conferred by various Masonic organizations or bodies, each of which operates under the control of its own central authority. In the Scottish Rite the central authority is called a Supreme Council.
The Scottish Rite is one of the appendant bodies of Freemasonry that a Master Mason may join for further exposure to the principles of Freemasonry. It is also concordant, in that some of its degrees relate to the degrees of Symbolic (Craft) Freemasonry. In the United States, the Scottish Rite is officially recognized by Grand Lodges as an extension of the degrees of Freemasonry. The Scottish Rite builds upon the ethical teachings and philosophy offered in the Craft (or Blue) Lodge, through dramatic presentation of the individual degrees.
Wikipedia does a good job of presenting factual information about the oldest known fraternity. This article provides content and links to the Wikipedia topic.