The Copyright Act gives all authors a set of rights that only they may exercise. These include the right to make copies, to prepare derivative works, to publicly distribute, display and perform the work, and in the case of digital sound recordings, to perform the works over a digital network.
With this short set of rights, you would have near perfect control over your works. So, the law provides some breathing room so the public can benefit from the increased numbers of works (this is the goal of the law). To use those works, the public enjoys rights to display their own copies, to lend them or give them away, even to sell them, and to reproduce parts of the works in certain circumstances, even to reproduce the entire work in some cases, as a fair use. For more information about fair use, consult the fair use section.
Your rights go on for your entire lifetime, plus 70 more years.
Your copyright brings the full force of federal law to your side to enforce your rights. The entire judicial system is at your service. For a price. It's really sort of odd that you have these rights whether you want or need them, but that's how it is. Your copyright exists from the moment you create original expression that is fixed in a tangible medium. It's automatic. You needn't register your copyright or even put a notice on your work.
In academe, we usually make our livings in other ways besides selling copies of our creative endeavors. We sometimes have to pay even to get our scholarly papers published. Only rarely do we make royalties from the sales of textbooks. So, really, we don't need quite this robust a set of rights attached to everything we do. We could get by with a much thinner copyright most of the time, one that mainly required that we be acknowledged as the author of our works. That's what matters most to us, typically. But we have the full panoply, whether we need it or not.
Unfortunately, the full panoply prevents many important educational and scholarly uses of our works because our readers believe that they have insufficient rights under fair use to use our works. Here's where we all, as authors, can say precisely what we are willing for them to do without our permission, and what our conditions might be. Creative Commons makes this easy. Read copyright management to learn more.
Trim down your beefed-up copyright. The public, educators, and your successors in your discipline will thank you for it.