Docker is hotter than hot because it makes it possible to get far more apps running on the same old servers and it also makes it very easy to package and ship programs. Here’s what you need to know about it.

All the noise is happening because companies are adopting Docker at a remarkable rate. In July 2014 at OSCon, I ran into numerous businesses that had already moved their server applications from virtual machines (VM) to containers.

Indeed, James Turnbull, then Docker’s VP of services and support, told me at the conference that three of its largest beta bank customers were moving it into production. That’s a heck of a confident move for any 1.0 technology, but it’s almost unheard of in the safety-first financial world.

Today, Docker, and its open-source father now named Moby, is bigger than ever. According to Docker, over 3.5 million applications have been placed in containers using Docker technology and over 37 billion containerized applications have been downloaded.

Why companies embrace Docker containers

So why does everyone love containers and Docker? James Bottomley, formerly Parallels’ CTO of server virtualization and a leading Linux kernel developer, explained VM hypervisors, such as Hyper-V, KVM, and Xen, all are “based on emulating virtual hardware. That means they’re fat in terms of system requirements.”

Containers, however, use shared operating systems. This means they are much more efficient than hypervisors in system resource terms. Instead of virtualizing hardware, containers rest on top of a single Linux instance. This means you can “leave behind the useless 99.9 percent VM junk, leaving you with a small, neat capsule containing your application,” said Bottomley.