Dave: 192.168.x.y is a local or private IP address, and there are three address ranges reserved for this purpose: 10.0.0.0 to 10.255.255.255; 172.16.0.0 to 172.31.255.255; and 192.168.0.0 to 192.168.255.255. The cheap Belkin router I have connected to this and another computer, plus a game system and a few Wi-Fi devices, allows me to select any of these three address ranges.
It's one of the reserved ranges for private IP addresses
Because it allows the lease amount of Addresses
Yes you can change them to any Private A, B or C Class address you would like:
A = allows Millions of hosts
B = allows about 65k
C = 256 Hosts
there are a lot more isps than just 192