Adobe Digital Experience Protection Technology (ADEPT) is the official name of Adobe's DRM scheme.
 Adept DRM
Adept DRM is used by many eBook devices and was the main DRM scheme prior to B&N's addition to the Adobe RMSDK. This DRM is applied to an ePub or PDF file. It is presently the standard Adobe DRM. (as of Feb 2010).
There is an older DRM scheme that was applied to PDF files. It is not compatible with the new scheme.
The Adobe Digital Editions software provided the initial desktop support for Adept DRM on Windows and was then extended to Mac OS X. Today a mobile version of this software is the leading PDF and ePUB software used on portable eBook Devices.
One of the features of this DRM scheme is that it supports time limited licenses making it useful for Public Libraries to use to checkout eBooks to their clients. Typically an eBook will be checked out for a short period of time, often 3 weeks, after which the license just expires. There is no need to return the eBook to the library or check it back in. Some systems may allow checking an eBook in early to free up the license.
This DRM limits the number of devices to 6 portable readers and 6 computers. Unfortunately some upgrades cause the computer count to increment limiting the devices to much less. This requires contacting Adobe to remove the old devices from the list.
 Barnes and Noble DRM
Barnes and Noble DRM is based on the original DRM available on eReader software. Barnes & Noble uses this DRM on their eBooks and made a contract with Adobe to add it to the Adobe RMSDK which is used to protect B&N books sold in the ePub format and eReader format as of December 2009.
It is an alternative to the Adept DRM ePub and will be available with the 4.0 release from Adobe. Devices which support this DRM will also support Adept DRM ePub unless they have explicitly disabled it. This DRM variant allows sharing, if enabled by the eBook publisher.
The generic name for this form of DRM is called "social DRM." This is not locked to specific devices. Instead it is similar to a user name, password scheme where the user name is your name and the password is a credit card number. Thus the same user can use an eBook on any of their devices. A recent addition to this scheme is the ability to loan the book out to another user for a fixed period of time, currently set to two weeks. This is similar to the idea of a library checkout however there is a limit to how often it can be done, currently set to 1, and requires permission from the publisher.