AMD64 is a 64-bit instruction set architecture developed by AMD that extends the earlier 32-bit x86 architecture. It allows for greater memory addressing capabilities, enabling systems to utilize more than 4 GB of RAM, which is a limitation of 32-bit systems. This architecture is widely used in modern computers, servers, and workstations. The AMD64 architecture is compatible with existing 32-bit applications, allowing them to run on 64-bit operating systems. It supports advanced features like enhanced security and improved performance for demanding applications, making it a popular choice for both personal and enterprise computing environments.