What is the difference between a cassette and freewheel?

[Guest]

What is really confusing me are the videos:
<a href="http://bikeride.com/replace-freewheel/">How To Replace A Freewheel</a><br />
<a href="http://bikeride.com/replace-cassette-cluster/">How To Replace a Cassette Cluster</a>
Why are there 2 videos for the same thing? What is the difference?
And what I really don't understand: when do you need the chain whip and when not?
Maybe you can do a new video and explain it all in one...
Johannes

[Alex Ramon]

Hi Johannes,
The difference between the two is explained here (at about 0:09):
http://bikeride.com/replace-freewheel/
And in the image below. Let me know if you still find it confusing...
<a href="http://www.sheldonbrown.com/freewheels.html"><img src="http://bikeride.com/images/bike/cassette-freewheel.jpg" alt="Cassette Freewheel" /></a>

[toekneebullard]

So judging by that picture, you either have one or the other right? You can't change without changing out your entire wheel, correct?

[Alex Ramon]

The difference is in the hub. As in the picture above, one has threads while the other has splines. To change between them you'd need to change the hub. So you don't need to change the entire wheel, but you'll have to at least re-spoke the wheel to make the change.