What Is The H-1B Program?

I keep hearing talk about the H-1B cap. What is that, and how does the H-1B Program work?
U.S. employers use the H-1B program to hire, on a temporary basis, highly specialized employees such as doctors, engineers, teachers, researchers in a wide variety of fields, accountants, medical personnel, and computer scientists. These unique skills and knowledge are said to be in short supply in this country, thus U.S. businesses use the program to alleviate temporary shortages in these specific occupations, and to acquire special expertise in overseas economic trends and issues, thereby allowing them to compete in global markets. U.S. employers also turn to H-1B professionals when they recruit post-graduates from U.S. universities. Foreign students represent half of all U.S. graduate enrollments in STEM subjects (science, technology, engineering, and mathematics). There still are not enough U.S. students graduating with advanced degrees in these fields to fill highly specialized positions, and according to the Bureau of Labor Statistics (BLS), the demand for such graduates will increase substantially in the next ten years.