IPv4 is controlled standard where IANA is one defining address ranges and assigns IP numbers to user (companies).
IANA defines 3 private ranges used only on Intranet or private use, not used on Internet. Ranges are called classes A, B and C and they are:
- A : 10.0.0.0 – 10.255.255.255 – used in big companies with lot of PCs (up to 16777216)
- B : 172.16.0.0 – 172.31.255.255 – used in smaller companies (up to 1048576)
- C : 192.168.0.0 – 192.168.255.255 – home and micro company usage (up to 65536)
Home routers usually come preprogrammed to 192.168.0.x or 192.168.1.x
Reference