IDE - click here
OEM - click here
So, your DVD drive would connect to your computer (motherboard) through the IDE connection/cable. All you have to do is disconnect your old one and reconnect your new one.
The OEM means, brown box, DVD drive and thats it really. If you know what you are doing then go for the OEM drive. If you've never changed a drive or even gone "inside" your computer then buy the "Retail" version of the drive where you'll get a shiny box, screws, connections, manuals...But of course always check the package contents ;-))