AMD and Intel are the major manufacturers, and VIA also supported it with VIA Nano processors. They call their own 64-bit processors AMD64, Intel64 and VIA x86-64 processors, respectively. Game consoles such as Microsoft Xbox One and Sony PlayStation 4 use their own semi-customized AMD64-based APU as main processors.
x64 is another name used to refer to 64-bit extended systems based on this kind of processors. People often use x64 to refer to its associated instruction set architecture and processor.