IPv4 and IPv6 are both Internet Protocol versions that facilitate network communication. The primary difference lies in their addressing capacity; IPv4 uses a 32-bit address scheme, allowing for approximately 4.3 billion unique IP addresses. In contrast, IPv6 utilizes a 128-bit address scheme, accommodating a virtually limitless number of unique addresses, thus addressing the exhaustion issue of IPv4. Additionally, IPv6 improves routing efficiency and provides better security features. The transition from IPv4 to IPv6 is crucial for future network growth and connectivity.