A "hop" has to do with network routing. If you are on a particular IP network, for example 192.168.1.0, and you need to get to 192.168.4.0, data must travel through a router.
…A router provides interfaces to join at least two distinct networks. If your data travels through only one router to get to a different network, that network is considered to be one "hop" away. Data moving through additional networks to get to the destination network increase the hop count by one for each router. Thus, in the above example, if the first router had an interface attached to the 192.168.1.0 network, and another interface attached to 192.168.2.0; and then if the next router had an interface on 192.168.2.0 and one on 192.168.3.0; and then if the next router had an interface on 192.168.3.0 and one on 192.168.4.0; then the data would travel through --one, two, three-- routers to get to the destination network. In this case, network 192.168.4.0 would be three hops away from 192.168.1.0. (MORE) 
