How To Control A Motor With A MicroProcessor

I'm just wondering how I can control a 24VDC/12VDC motor with my microprocessor board from parallax. Since these motors require a lot of amperage, the power the microprocessor board produces will not be enough, so I need to create something like in the attached image.

Basically, if I push a button, that sends a signal to close the switch which completes the circuit. I'm just not sure what electric components I need to do this since it requires like two circuits working together.

This is a thing transistors are very good for, a little current in at their base and a lot of current goes between the collector and the emitter. If you want a prepackaged solution look up motor controller.