PS:How is it different from regular computers with multiple processors?
On a regular computer, a bit can be 0 or 1. Electrons over there means 0; electrons over here means 1. On a quantum computer, a bit can be 0, 1 or both. So in your quantum computer, one qubit means two things at once, or with two qubits, four things at once, or three qubits, eight things at once.