we basically use the networks ending in the subnet /8, /16 and /24. For example, 10.0.0.0/8 is a biggest network containing the address from 10.0.0.0 to 10.255.255.255 (more then 16 million addresses in the /8 subnet).
10.0.0.0/16 is a smaller subnet mask, containing the single IP addresses from the range between the 10.0.0.0 to the 10.0.255.255.
10.0.0.0/24 is the smallest subnet mask and containing the addresses between 10.0.0.0 to 10.0.0.255 only.
