Private IP addresses are not valid on the Internet whereas, public IP addresses are valid as nodes on the Internet. They can be resolved and routed across the Internet from one point to another unlike private IP.
The following IPv4 address ranges are reserved for private networks:
Class A network:
10.0.0.0 - 10.255.255.255
(10/8 prefix) range
Used for large network that requires a bigger pool of 16 million private IP addresses
Class B network:
172.16.0.0 - 172.31.255.255
(172.16/12 prefix) range
Used for medium-sized network that requires 65000 private IP addresses
Class C network:
192.168.0.0 - 192.168.255.255
(192.168/16 prefix) range
Generally used for IP range on smaller network for easier addressing of 254 IP addresses.
Note: 169.254.0.0 range is allocated to client when they fail to obtain address from a DHCP server.
Refer to RFC 1918 for a complete description for Private IP addresses
