DRM (digital rights management) is simply an electronic way of ensuring that the aforementioned digital copyright can be preserved by the owner of an intellectual property - be it a hardware maker, software designer, publisher, artist, etc.
Purchasing digital media does not grant said Joe or Joanna Consumer the right to do whatever he or she may choose to do with their purchase(s) - contrary to what the dude trolling the parking lot with a CD organizer bursting with two dollar copies of shaky-cam versions of theater movies may lead you to believe. But it also doesn't mean that your average, everyday multi-billion dollar corporation is only trying to protect the pennies-on-the-dollar royalty that artists and designers earn from the very wares that said corporation sells for an astronomically high markup price (that they, in turn, can reap millions from) either.
Does piracy really affect the bottom line of the Amazon's of the world? Though they'd like for you to believe differently, that's highly unlikely at this particular point in time; while those determined to pirate something will almost certainly find a way to do it, they're still far outnumbered by the average, everyday consumer who will shell out the coinage necessary to pay for the price to play.
DRM is far from the demon that the anti-control types try to paint it as. But the circumvention of DRM may actually affect a supremely talented starving artist type whose bottom line may be compromised by the unauthorized version of his eBook that has been posted for sale on your favorite torrent site.
Regardless of how you may (or may not) feel about it right now, I'd advise you become informed about DRM sooner rather than later. As the world moves progressively farther down the path to all things becoming digital and content-driven, it's more important than ever to read before you buy.
Digital copyrights sure as heck aren't going anywhere anytime soon; that much I can guarantee.