DRM schemes for music and video - how do they work, in practice?

There have been a couple of threads recently about portable media players, compatibilities with various types of file and the complexities of converting files from one format to another or changing things like the volume level of music in files with Digital Rights Management.

Although I do quite a lot of work involving the manipulation of audio and video content on computers, none of this has really involved anything with DRM, so I thought it would be useful if someone in the know could describe the practical operation of various DRM schemes.

NOTE: I’m not looking for technical information that could be used to defeat the schemes - I’m hoping for something that describes what an end user of the product would experience and be permitted to do in terms of backing up and restoring the files as data, moving the files from one machine to another when upgrading, copying the files to a portable player (and using them on it), copying the files to a different portable player after upgrading, making ‘comfort adjustments’ to the content - such as increasing the volume level of audio, or the contrast/saturation of video.

Also, can we steer away from “xyz company sucks because…”. Please keep it factual.