They are talking about the OSI model layer. I recommend looking into Network+ material, don't do the exam, but I learned quite a lot studying for the exam usin

They are talking about the OSI model layer. I recommend looking into Network+ material, don't do the exam, but I learned quite a lot studying for the exam using the CBT Nuggets videos. Also, Cisco has the ICND1 and ICND2, or rather called CCNA, which goes into depth on network technologies. If you're more on the Web technology side, I recommend looking at this book called "HTTP: The Definitive Guide" By far it was one of the best books I studied in undergrad, it goes over a lot of Network protocol fundamentals.