How to use arduino to trigger something else

Hi, i am very new to arduino, and i had a question. I have a motor that needs 12 volts, which arduino obviously can’t provide. What do i use as a electric “switch” so that when i feed the switch 5 volts, it will allow a 12 volt battery connect to the motor?

See:- http://www.thebox.myzen.co.uk/Workshop/Motors_1.html