What is the difference between IPv4 and IPv6?

IPv4 uses 32-bit addresses (4.3 billion possible addresses), written as four decimal numbers (192.168.1.1). IPv6 uses 128-bit addresses (3.4 x 10^38 addresses), written as eight hexadecimal groups (2001:0db8:85a3::8a2e:0370:7334). IPv6 was created to address IPv4 exhaustion and includes features like simplified headers, built-in IPSec, and no need for NAT. Transition is ongoing with dual-stack and tunneling approaches.