The Digidesign iLok is a simple device that is designed to prevent piracy with plug-ins and other software. You will need one of these to run most plug-ins in Pro Tools and in other DAW's. I've had one ever since I got Pro Tools a number of years ago, as it's absolutely necessary unless you're not going to run any outside plug-ins, which isn't going to be many people. You sync the iLok up with an online account that has all of your plug-in licenses on it. The iLok itself doesn't contain any software information other than the license itself, so if you want to use a plug-in on any given system that you have an authorization for on your iLok, you're going to need to install it there. I say this because it's not like you can just bring your iLok from place to place and run the plug-ins, as the software needs to be installed on any system where you want to use it. Generally I use my iLok with my lap top in my home studio, as I don't think I've ever used it on another system. Having said this, it's definitely possible to use it in different studios if the plug-ins you have are installed on there, but if they already are, chances are that the plug-in is already authorized with another iLok on site. The iLok costs about $40 US dollars, which isn't too bad I guess, but it's not really something that you have a choice in buying if you want to run plug-ins that require this, which is really the vast majority of plug-ins out there. There are a few companies that don't require you to use an iLok account, but all of the major ones do. If you're looking to get into the plug-in game, having an iLok is the first step...