I found this great article below in Dog World that explains Schutzhund very well and with much details, so I hope this helps. The article below was found in Dog Worlds December 2001 issue. This article is titled Understanding Schutzhund and the author is Sharon Pflaumer.

Schutzhund is a performance event that tests a dog's character, intelligence, courage and athleticism. Titles can be earned at three levels: Schutzhund I, II, and III (abbreviated SchH I, etc). To earn a title at each level, a dog must demonstrate proficiency in tracking, obedience and protection work by successfully completing a series of exercises in each phase in a single trial. The dog must also score a minimum of 70 of the possible 100 points in each phase.
The eight exercises for the SchH I title for the obedience phase include on- and off-lead heeling, a walking down with recall, and retrieving a dumbbell on the flat and over a jump. The dog also must pass a test for gun shyness.

In the tracking phase, a dog must follow a track that is 300 to 400 pases long with two 90-degree turns. He must find two articles dropped on the track by the handler. (An article is a small object having the handler's scent.)
In the protection phase, the dog must protect the handler in a controlled manner. Several blinds are set up on the course. A helper hides inside one. (The helper wears protective clothing and a padded sleeve. He also carries a padded stick.) The dog is sent to search and empty blind. He must look to see if the helper is hiding in it, then return to the handler. The dog is then sent to a second blind where he finds the helper motionless and unaggressive. Now, the dog must guard the helper and bark a warning to the handler, but should not gripped the helper's protective sleeve. The dog is heeled to a third blind next. As the handler and the dog approach, the helper comes out in an aggressive manner, waving the stick as if to attack the handler. This time, the dog must immediately defend the handler by gripping the padded sleeve. The helper does his best to intimidate the dog until the judge indicates he is to become motionless and unaggressive. At this point, the dog must release the padded sleeve. If he doesn't after three commands, the dog fails.

Successive levels of Schutzhund competition require more precision on the more difficult work in all three phases. And dogs can also earned individual titles in tracking work.

Before a dog can compete in a Level I Schutzhund trial, he must be prequalified. (Due to an agreement between the AKC and the SV, all AKC-registered dogs are eligible for Schutzhund competition in this country.) To prequalify, he must earn the International Companion Dog degree (BH) by successfully performing another series of exercises. The BH is divided into two parts. The first tests the handler's control of the do with formal obedience in a ring. The dog must perform the first five exercises from Level I Schutzhund obedience. The second part tests the dog's character and is performed on the street or in a marketplace. For example, as the handler heels the dog through a crowd, a person participating in the test approaches him, says hello and shakes his hand. If the dog is fearful or aggressive during the exercise, he fails. Several other exercises test the dog's character in real-life situations. Temperament is further tested by the judge at the beginning of every Schutzhund trial.

All the available American and international titles can create a confusing alphabet soup. United Schutzhund Clubs of America offer an extensive list of titles and what they mean at www.germanshepherddog.com/aboutusa.htm