Memristors are any device whose resistance changes in response to the voltage that's gone across it in a predictable and reversible way. The phase-change memor

Memristors are any device whose resistance changes in response to the voltage that's gone across it in a predictable and reversible way. The phase-change memory they describe is one type. Memristors can form any logical gate. They are essentially resistors whose value can be changed dynamically and persistently. Rather than having them store data directly (which you can do, sure, and we'll probably see devices doing that soon) they can form logic gates in much the same way transistors do - except they can be changed in configuration while running. They can form a set of gates that function as a traditional memory latch one nanosecond, then the next be part of an adder. It's like if re-programming was so profoundly free on an FPGA as to be exactly as burdensome as performing an AND.