Babun is a shell, meaning that it can be used to run many different command-line programs. There are many pieces of Linux software designed to be used with Cygwin, another shell. Some of these are as simple as games, but the difficulty of getting your average shell up and running is a large barrier to entry. This shell makes it very easy, and provides some additional features, to boot. Plus, it's free!
No need for the nitty-gritty
Let's put it this way: Babun provides Cygwin functionality with little to no setup if all you want to do is run an ancient UNIX-based game. For those who do want to make more use of the shell's provisions, and have a Linux-lite environment running right on their non-Linux desktop, there's a package manager called pact, proxy support, plugins, and high-end xTerm compatibility. Whether or not these mean anything to you, they're there, and make the shell incredibly easy to use. The only drawback is that it isn't compatible with some older Cygwin addons, but in most cases this won't matter.
Don't run away, run software
Babun is a great choice for beginners and intermediate users alike, who can benefit either actively or passively from its many features. Beginners will appreciate its ease of use more than anyone, though.