DRM = Digital Rights Management.
That is, essentially, encrypting the text so that it will only work on one device, once.
Let me tell you a story about DRM.
A while back I rented a couple of DVDs at my local video store. I went to watch them on my computer (as I generally do, rather than take over the family TV/DVD player/game station).
One of them worked, no problem. The other didn't.
After an entire evening of trying, I finally got to the TV and the dedicated DVD player to watch the one that didn't work (I'd actually thought the disk was faulty). Turned out that it was broken to create that DRM. What did I do? I praised the movie that didn't have DRM (in addition to the rental fee, my beloved bride got me a copy as a prezzie, more money for the film makers) while I
panned the movie with the DRM (not only a loss of income from a purchase, but lost income from anyone who decided not to rent it based on my words).
Funny thing? I could have had either of those movies, free, no money to anyone, inside of a couple of minutes, if I'd decided to go the pirate route.