Classes allow for more people to have addresses despite having limited IP addresses. These classes are defined by the first three numbers in the IP address. Classes are defined by their leading bit’s where Class A has a 0 as a leading bite class b has a 10 and so forth. There are a total of 5 classes but only classes A-C are publically used for consumers such as you and me.

IPv4 Classes
Class	Number of hosts Per	Number of Networks	Start- end Address	Total Addresses
Class A	16,777,216 (2^24)	128	1.0.0.0 - 127.255.255.255	2,147,483,648
Class B	65,536 (2^16)	1933	128.0.0.0 - 191.255.255.255	1,073,741,824
Class C	256 (2^8)	1933	192.0.0.0 - 223.255.255.255/td>	536,870,912
Class D (multicast)	Not defined	1933	224.0.0.0 - 239.255.255.255	268,435,456
Class E (reserved)	Not defined	1933	240.0.0.0 - 255.255.255.255	268,435,456