About Different Types of Visas For "Business" vs "Work" In the U.S.?

Maybe I'm using the wrong terms, but I'll try to explain the differences between what I call a "business" visa, and a "working" visa to make my question clear.

A friend of mine is a securities (stock and bond) analyst in the U.K. He wants to come to the U.S. to research a company, call it IBM, that his U.K.-based firm is thinking of investing in. Here he'd meet with executives of IBM, visit a few plants, ask some questions, etc. After he was finished with the American "leg" of the process,he'd go back to the U.K., write up his report, and make his recommendation to his U.K. employer, who pays him there. I assume my friend would need what I call a "business" visa to come to the U.S. for this purpose.

Contrast this with a U.K. citizen who has accepted a job offer from IBM to work in the U.S., and he'll be paid here by the U.S. employer. I would imagine that he would need to go through a much more stringent process to get what I call a "work" visa, which IBM would probably help him get.

What exactly are the two different types of visa, and how do the requirements differ? Or how do I tell one from the other?