Norv Turner is one of the disciples of the 'West Coast Offense'. It has some parallels with the German Blitzkrieg. Back in World War I on the Western Front the two front lines slugged it out; each side expending incredible effort over a few scant yards. To have strong front lines was everything. After the end of the first World War the French took this lesson too much to heart and built the Maginot line, a string of concrete bunkers with heavy artillery and ample protection for the infantry. But they didn't run it across the Belgian Border; and the trouble was once an enemy got behind the line, it was impotent. The Germans pierced the French lines with an armored assault going through forest thought to be impassible by tanks, once behind the lines these fast armored formations created chaos; shattering the French defenses in less than six weeks, something they were unable to accomplish in four long years in the first World War.
The standard offense sought to establish a running game first; after the running game was drawing players closer to the line of scrimmage to stop the run, teams would go to the air. Very similar to the static first world war, making those hard fought yards on the main line was everything. The West Coast seeks to flip that on its head; the object is to start with short passes that go over the line and have big tight ends and receivers bust tackles and make yards after the catch behind the line. These quick passes will often come off of a short three step drop by the quarterback, making it very difficult to get a sack. One archetype formation will line up the five lineman plus the tight end in front, have two runningbacks in the backfield on either side of the quarterback and two receivers on the outside. Sparing no expense I have created the following diagram to amaze and confound you:
The quarterback is the key to the offense. Before or within the three steps he must make his three primary reads on the three receivers, if they are covered he will go to a check down receiver (one of the two running backs). The runningbacks can either stay back in pass protection if the defense sends the blitz or go out for the short route. Finding a quarterback that can make those quick reads and pass the ball accurately is the key for this offense. After the offense establishes itself with the short passes the defense will usually start tightening its coverage on receivers and the offense will begin to stretch the field with deeper routes and take advantage of bigger gaps in the line of scrimage with a power running game. While mostly associated with the three step drop, it does get run with longer drops and even from the shotgun.
The power running game also comes into play after hopefully establishing a lead in the first half to run the clock in the second half. In this type of offense it is important that your backs be able to catch well; one of the likely reasons Lorenzo Neal was released was his poor catching ability. Bill Walsh in San Francisco emphasized the short pass horizontally to spread out the defense and open up lanes for running and vertical plays.
Receivers generally need to be sure handed and good at catching in traffic. They also have to be extremely disciplined route runners as these shorter pass plays are often timing routes, meaning that the quarterback just throws to where he expects the receiver to be. With the timing route both the receiver and the quarterback read the defense and do a timed route where they both know how long the three step drop takes and how far the receiver can go on his very precise route. In some cases the quarterback will throw the ball without even seeing the receiver. Note that this can lead to odd results if the quarterback makes one read and the receiver another; the ball can end up not remotely close to a receiver; or even straight to a defender where no receiver is.
Another thing often done in the WCO is scripting the first group of plays; often fifteen or more. This scripting allows the offense to rehearse these plays over and over and get very precise in execution. It also leads to a certain unpredictability as the plays go off in the same order regardless of the position on the field; so you might see a stretch play on third and one. Sometimes Turner adheres too strongly to this for my taste; if the offense is off track fifteen plays can be a long time.
That is a general overview, but there are a few details that folks quibble over. As it is used now the WCO usually refers to the loose pass first philosophy. Technically the first West Coast Offense was run by Sid Gilman and subsequently continued by Don Coryell. Al Davis moved it to the Raiders as well. It comes with nomenclature that identifies the plays and formations. Bill Walsh was known for a particular brand of the WCO that emphasized the horizontal stretching to create running and passing lanes. Purists will argue that it isn't really a WCO, but just gets lumped in because Walsh coached the 49ers. The real key is to get beyond those static lines where every yard is measured in blood and sweat; this offense wants to break beyond and stretch those main lines so that you can create chaos in the backfield.