CIDR (sometimes called supernetting) is a way to allow more flexible allocation of Internet Protocol (IP) addresses than it was possible with the original system of IP address classes.
CIDR stands for Classless Inter-Domain Routingwas created back in 1993 because IPV4 was slowly running out of IP addresses, that's when IPV6 was created hoping to solve this problem. Although IPV6 is still not widely use, more appliances/devices now support IPV6 Protocols so if need be, people would be able to implement this new standard. IPV4 is a 32-bit standard vs 128-bit for IPV6 which gives us an almost unlimited range of addresses.