Neverhavemoney

Hey everyone i was just reading an articale in Maximum PC and it was how a hacker works.
It said that people will make an iframe to a website. Instead of going to the original website, you will be redirected to a fake website that is an EXACT replica(they probably just copy the source code). But i want to know is how they can redirect you. If you are going to a website, how can someone take you somewhere else. Did they hack the original? Or do they stop the traffic and pull it to there own site. I just want to know how this works. Remember, we are here as the good guys and i trust everyone on this site to do the right thing and not do anything to ever harm anyone. I want to know how they do it in general. I dont need steps on how to do it, that would be just wrong
Thanks again,
Ben