Who are these employees who install new computers, keep the corporate network running and help other workers reset their passwords? Cultural stereotypes about nerds with pocket protectors aside, what do we know about the people who keep the bits flowing and the digital lights on?

For instance, the IT guy—and they're about three times more likely to be men than women—doesn't necessarily have a computer-science degree. About a third come to IT with degrees in business, social sciences or other nontechnical fields. More than...