IPv4 and IPv6 are two versions of Internet Protocol. IPv4 uses a 32-bit address scheme allowing for a total of about 4.3 billion addresses. Due to the rapid growth of the internet, IPv4 addresses are becoming scarce. IPv6 was developed to solve this problem, using a 128-bit address scheme, which allows for a significantly larger number of devices to be connected to the internet. IPv6 addresses are also alphanumeric, longer, and are separated by colons, making them structurally different from IPv4 addresses.