Name: Mad-Eye Moody
Age: Unknown.
House: Unknown
Distinguishing Characteristics: Moody gains his nickname from the magic eye that gives him a distinctly unsettling appearance: while one of his eyes is small, dark, beady and relatively normal, the other is large, perfectly round, and a vivid shade of blue. While his real eye behaves normally, the magic eye is unblinking and constantly rotating, taking in everything around it. Moody also has part of one leg missing, which has been replaced with a wooden stump. Underneath his thick mane of dark grey hair, his face is little more than a mish-mash of intersecting scars and has the appearance of badly weathered wood. A large chunk of his nose is also missing. All of these things are the products of his time spent as an Auror and a testimony to his countless fights with the agents of Voldemort.
Heritage: Unknown.
Family: Unknown.
First Mention: Chapter 11 of Goblet of Fire.
General: It is ironic that nearly everything that is known about Alastor Moody has been learned from someone impersonating him, along with a number of things said about him by his friends and colleagues. The real Moody has provided very little additional information about himself.
The first definite information known about Moody was that he was an Auror and member of the first Order of the Phoenix in the 1970s. He was already aging at that time, as his hair was grey in the picture of the original Order that he showed Harry in August 1995 - that picture was taken sometime in the late 1970s, and so it can be assumed that he was already in his fifties by that point. Hence, he is in or approaching his seventies by the end of OotP.
This would mean that Moody probably attended Hogwarts in the late 1930s and may even have been a pupil at the same time as Tom Riddle and Rubeus Hagrid. He must have been a gifted student and done very well in his exams to go on to become an Auror. After passing his NEWTs, he would have gone on to the three years of training with the Ministry of Magic before becoming fully qualified.
Moody was renowned in the 1970s as the most bring-them-back-alive of all Aurors, preferring to bring his Death Eater targets to justice rather than using Unforgivable Curses even when authorized to do so. Most of his injuries are a direct result of this attitude, but his bravery ensured that he was responsible for apprehending a large number of Voldemort's supporters. He was certainly capable of defending himself, however, and Evan Rosier for one found out to his cost that if it came down to a fight to the death, Moody was not prepared to give any quarter.