They are used for gripping right around the periphery of any disk or ring shaped work-piece.
A conventional 3 jawed chuck will destroy the teeth on a wheel for example if you try to hold it to bore out the centre.
There isn't a lot of gripping surface so using one for something with a lot of overhang isn't a good idea. ( Unless also using the tail-stock).
The distance between steps is the same on all 5 but each starts from a slightly different place. So if you can't find a suitable holding place on the first chuck you work your way through them all until you do.