Well, if you head on over to Fictionwise, they have an
"About Multiformat and Secure formats" page which has information on what each type of DRM can mean.
And if you go look at a particular secore ebook entry then you get information about he restrictions on that book. For instance,
Eric by Terry Pratchett says:
Code:
Secure Adobe Reader 7: Printing enabled, Read-aloud enabled
Other formats: Printing DISABLED, Read-aloud DISABLED
Does that help?