This is the best explanation we've heard for why Docker has become such a hot startup

Last year, a tiny startup called Docker rose from obscurity to capture the hearts of the whole tech industry.

Less than two years after its founder Solomon Hykes awkwardly previewed his creation at the PyCon conference, the biggest names in tech were on their knees asking it to be their partner: Amazon, Dell, HP, Google, IBM, Microsoft, Red Hat, VMware, etc.

Why? It was hard to explain. Literally.

Docker makes a tech called a container. And thanks to Docker, containers have become so popular that there's a war going on between Docker and other would-be Dockers over this new container market. Contenders include another hot Valley startup (and former close Docker partner) CoreOS and Google, just to name a few.

Containers add management features to cloud applications so coders don't have to deal with all that stuff themselves. (And yes, that's the explanation for non-geeks. Docker explains it like this: "Docker is an open platform for developers and sysadmins to build, ship, and run distributed applications.").

But we didn't truly understand why developers were going so nuts for it until we talked to Todd McKinnon, CEO of Okta and former star engineer of Salesforce.

Okta offers a cloud service that helps enterprises manage employee passwords and accounts to other cloud services. Although many of his customers use Docker, Okta doesn't particularly have to support it.

But Okta's development team loves Docker, he says, for a very simple reason: They can write code on their laptops, test it there, and when they publish it to their servers in the cloud, it works the same as it did on the laptops, McKinnon told us.

That didn't happen before.

Before Docker, "code would run in a laptop and you'd think you got it working, but then something is different on the server, not the right files or configuration or something, and it would break."

Then you'd spend the rest of your day trying to figure out what the problem was.

Fixing that awful problem is wonderful enough, but the cherry on top is that Hykes was really clever about it. He used a simple feature in Linux that had been there for years and turned it into a cloud service of its own.

"It's really cool. A good example of innovation. Developers were sick of doing this and Docker built this cloud service and solved it," McKinnon says.

Now, many developers won't write code without Docker and won't send their code to a cloud service that doesn't support Docker.

And while we're sharing things that McKinnon explains well, we'll toss this one in, too, just for kicks. Okta is pronounced "Ah-kta" like "octave," not "Oh-kta" like "Okra." Just sayin'.