I can recommend several resources: use www.acronymfinder.com heavily. All you have to do is type in the acronym, and it will show you pretty much all known expansions. Likewise, you will find the TechWeb encyclopedia at http://www.techweb.com/encyclopedia/ helpful, as well as http://www.techfest.com for more in-depth coverage of networking topics. Don't forget to use http://www.searchnetworking.com to help you figure stuff out, either.
Since you didn't tell me exactly which book you're working from, I will take the liberty of recommending my own Networking Essentials textbook from Course Technology (ISBN: 0619034505). Although Amazon gives it a middling rating of 3.5 stars, it's been adopted as the introductory textbook for networking classes in over 300 schools all over the US and Canada. I think you'll find it a pretty accessible book that will help you learn what you need to know to make sense of your course textbook. OTOH, if you'd rather stick closer to your topic, search on Amazon for Network+ titles and buy the highest-rated book that gets good ratings for readability. That should help immensely. For my part, the Michael Meyers (Osborne/McGraw-Hill) and the David Groth (Sybex) both get very high ratings and I've had good experiences with both books - but then, I know this stuff already!
This was first published in July 2002