Hello HolyRoyal,
Endpoint Discover functions the same as Network Discover, that is it provides the ability to discover items on an Endpoint (laptop and/or desktop).
Endpoint Prevent provides an agent that musgt be installed and deployed on each endpoint (desktop or laptop) you are lookign forward to protecting. Endpoint Prevent deals w/ the content of the file in a protection point of view. Within DLP for Endpoint Prevent you can block items such as the clipboard, write to removable media, email within Outlook, web pages even if HTTPS through Firefox and IE. All kinds of other optiosn as well. This is a video I created on DLP on the Endpoint, I think it was version 11.1 but 99% of it is still valid: http://vimeo.com/album/1612870/video/24592234
Let me know if there are other questions you might have and feel free to email me as well.