"Linux was created on the first 32-bit CPU in the x86 CPU family, the 80386. Since then, computing has evolved substantially, and while 32-bit computing remains adequate for many purposes, its days are nearing an end. Increasing demand for RAM will soon dictate a shift to 64-bit architectures.
"Fortunately, 64-bit CPUs are currently available and are beginning to move into the mainstream. One of these architectures, AMD's AMD64, is gaining in popularity, and seems likely to dominate the market currently held by its Intel Architecture-32 (IA-32, or x86) predecessor..."
