This is to augment the somewhat sketchy information on DNS and reverse lookups in the network layer chapter.
For this discussion, we will concentrate on how the DNS maps host names to IP addresses and vice versa. We'll stick to IPv4 addresses for the sake of my sanity and overall clarity, but in case you're wondering, the mechanisms for IPv6 are quite similar, just a little more convoluted (like pretty much everything about IPv6).
In case you're familiar with the conecepts of DNS in general, and reverse lookups in particular, you can skip the following section. If not, please read on.