The Vyper is a single channel esc. Meaning, 1 input channel, 1 voltage regulated channel out.

The older and no longer sold Sidewinder is 2+1 input channels, 2 voltage regulated channels out.

In short. 1 Vyper does 1 motor or side of your machine.
(if you want to build a heavyweight machine with 4 Robot Power Magnum drives each side, 1 Vyper can control the 4 Magnums with a reasonable rate of succes.)