Virtual Machine
I mentioned that the Dalvik's full name is the Dalvik Virtual Machine.
Let's look at what a virtual machine is - simply put - that's a software computer inside of a computer.
In the PC world a famous example is a thing called Virtual Box - it's an app - install it on your PC or Mac and it emulates a PC, into which you can install another operating system.
I'm typing this on a Mac right now. I have two windows on my Mac, inside one is a full copy of Linux and inside another is a full copy of Windows XP. Both Linux and WinXP think that the Mac that they're really on is just another computer on their same network.
I'm not _emulating_ (pretending to run) Linux or Windows and I'm not dual-booting -> I'm actually running those two operating systems at the same time as Mac OS X, inside of virtual machines.
Because software believes whatever you tell it - tell it that its environment is a computer, it believes you - even if it's really a made-up computer in software.
Javascript, Java and the JVM
As you know, your browser runs Javascript - simple applets made to run on a browser. The next step up are Java programs - they run on nearly anything, just like with a browser, not caring if on Win, Mac or Linux.
But in order to run Java programs on your desktop (nearly everyone in fantasy football does this to keep track of their teams and leagues) you install the Java Virtual Machine (JVM) on your PC.
The JVM isn't all general-purpose and a blank piece of paper like Virtual Box - it's a virtual machine designed to run only Java apps but on any choice of operating system.
The Dalvik Virtual Machine
You may be aware Android apps are written mostly (+90%) in Java, the rest in "native" code (C/C++).
The DVM is like a mobile JVM except - 1) runs only on an embedded Linux with Android mods to the Linux kernel (the lowest piece of software on your phone or PC - the thing that makes all the other pieces work) and 2) it can run Android-Java or native apps.
It's one of the most advanced virtual machines ever dreamed up.
What the Dalvik allows that nothing else does
Droid Den