SAN FRANCISCO — This year, Netflix made what looked like a peculiar choice: the DVD-by-mail company decided that over the next two years, it would move most of its Web technology — customer movie queues, search tools and the like — over to the computer servers of one of its chief rivals, Amazon.com.

Amazon, like Netflix, wants to deliver movies to people’s homes over the Internet. But the online retailer, based in Seattle, has lately gained traction with a considerably more ambitious effort: the business of renting other companies the remote use of its technology infrastructure so they can run their computer operations. In the parlance of technophiles, they would operate “in the cloud.”

Ah, the cloud — these days, Silicon Valley can’t seem to get its head out of it. The idea, though typically expressed in ways larded with jargon, is actually rather simple.

Cloud providers, large ones like Amazon, Microsoft, Google and AT&T, and smaller ones like Rackspace and Terremark, aim to convince other companies to give up building and managing their own data centers and to use their computer capacity instead.