ok this is the netmask for a particular network.
the 192.168 is the network part and the rest is the host part but it's restricted by the netmask.
generally it's in this format
address/prefix-length where the prefix-length is the number of bits in the network portion of the address.
In your case the network portion has 16 bits(2 bytes).
IMPORTANT
well I think this is not compatible with Natural Mask (coz 192 starts with 110 in its binary representation) so the natural prefix-length is 24 and the network portion should be like this 192.168.x/24
look at
this RFC for more information about network subnetting and masks
