Containers: A new and better kind of code?

From the NYTimes:

Docker is at the forefront of a new way to create software, called containers. These software containers are frequently compared with shipping containers. And as their popularity grows, building big computer networks could become remarkably simpler.

Like the big metal containers that can move from ship to ship to truck without being opened, software containers ship applications across different “cloud computing” systems and make it easy to tinker with one part, like the products for sale on a mobile application, without worrying about the effect on another part, like the big database at the heart of the corporate network....

“It’s a huge efficiency gain in how you write code,” said Mr. Golub, who started his career teaching business courses in Uzbekistan. “You don’t have to rewrite everything, then fix all the breaks when it goes into production. You just work on what you change.”

Tell me more. This tells me a little more:

DotCloud, the precursor of Docker, was in the business of helping developers build online applications by focusing on things like spreading use across several computers.

“Software developers need to be able to work easily with complicated infrastructure,” said the company’s founder, Solomon Hykes. “It was clear that cloud applications would have to be written efficiently, become part of the Internet, update constantly, and be always online, for all kinds of industries.”

DotCloud was one of many such services, and could not find many customers. But there was a container-type function in DotCloud, like the one Google had built. Mr. Hykes, who was talking with Mr. Golub about what the company could do to generate interest, worked at building a way for one container to work over the many versions of the Linux operating system.

What this is telling me is that we've got a new way to break big programs into (quasi)independent blocks. That's nice, but what's new about it aside from its newness?