Basically a midi keyboard like the pro49 you pointed at is a special kind of midi controller. Because you have midi controllers that are no keyboards either.

But first let's answer your question. Keyboards like Casio's/Yamaha's/Whatever in that kind's are not only meant to be connected to a computer. They can be played standalone (they have an intern sound generator). Basically, you can make sounds with those keyboards without anything else. But the more advanced ones have midi in/out/(thru if even more advanced) so you can control midi hard/software, or the intern sound generator can be controlled over midi.

A Midi keyboard is basically just a controller. It's meant to control midi devices over the MIDI controller. If you only have such a keyboard, you're nothing with it, it can't make sounds out of itself. You need hardware (sound module, synth module, whatever that accepts midi) or software (softsynths, a sequencer that accepts and passes through midi,...). That's the big difference.

Now about the other midi controllers. A basic midi keyboard does just what it is intended for : pass on note information (so you can play notes). More advanced (read most actual keyboards) also have a pitch wheel and a modulation wheel (can also be a joystick or a ribbon) so you can do glides and control a certain parameter for modulation.
Now the problem is, many people still prefer to twist/press /knobs buttons than to control those same knobs/buttons virtually with the mouse. That's why you see more and more midi controllers around that are not keyboards. How they look depends what they are designed for, but to simplify let's say the most advanced ones roughly look like a mixer : faders, knobs, ... When you move a fader on that controller, a fader in your software moves...

So which one to buy? Good question. If you just want to input notes, the pro49 is a good choice. But like I said, many people prefer touching real hardware knobs, maybe you are like that also, so take a look at the mk249c² (same keyboard, but has some knobs that can control other parameters in your instruments, I have that one, it's pretty good). It doesn't cost much more and adds a lot of ergonomy.
Be aware that evolution has been bought over by M-Audio (they were the main concurrent in that range with their Oxygen-8 keyboard).

If you're not afraid to spend a little bit more, I suggest you take a look at the Novation Remote 25 which is excellent (build quality, ergonomy, features, it has it all).

Thanks for the help.

So can you just hook up the midi controller to the computer and play? Assuming I do have it hooked into my sound blaster audigy?

___________________
-Jon
www.DJjoncaserta.com - - mixes and whatnot (melodic progressive house and trance)

Well depends. My evolution came with a DIN 5 pin to gameport connector (most consumer soundcards have their joystick port doubled as midi port. I don't remember what the audigy uses, you might check that out), and with a usb cable.

If you have a modern computer, it's better to use the USB port. With USB it's plug it in and play. Of course you need software than uses midi (sequencers, softsynths than integrate into sequencers or work standalone). Usually if you use the USB way, once it's plugged in, you can choose it as input in your software as USB Midi In. The USB has a nice feature that it can send midi data back to your evo keyboard, and the evo can output that midi data through it's midi out.

If you connect it to your soundcard (so I repeat, if you have the gameport on your soundcard you're set, if you have a more pro card, it will feature a DIN5 connector also, a din5 to din5 cable does not come with an evo). To use this you must be sure your soundcard is well installed (usually the midi port has an apart driver, but in actual OS'es it is installed right away). When plugged in, you select the midi input of your soundcard.