What is the custom function(p,a,c,k,e,d) used for?

So if you use http://matthewfl.com/unPacker.html as I posted in the comments, it "unpacks" the code into this:

(function()
    {
    var b="some sample packed code";
    function something(a)
        {
        alert(a)
    }
    something(b)
}
)();

It doesn't seem to be malicious. For a soft argument on why you would use this, see javascript packer versus minifier:

Packed is smaller but is slower.

And even harder to debug.

Most of the well known frameworks and plugins are only minified.

---

Packer does more then just rename vars and arguments, it actually maps the source code using Base62 which then must be rebuilt on the client side via eval() in order to be usable.

Side stepping the eval() is evil issues here, this can also create a large amount of overhead on the client during page load when you start packing larger JS libraries, like jQuery. This why only doing minify on your production JS is recommend, since if you have enough code to need to do packing or minify, you have enough code to make eval() choke the client during page load.

---

Minifier only removes unnecessary things like white space characters where as a Packer goes one step further and does whatever it can do to minimize the size of javascript. For example it renames variables to smaller names.

It's a function which decompresses compressed/obfuscated javascript code. Many JS libraries and scripts make use of it.

There are online tools where you can pack and unpack code via the browser, which use the function.