If you are bottling then gelatine isn't a great idea, if you use a secondary and let the yeast drop out there then you will have minimal yeast left for bottle conditioning.
If you are bottling though the yeast doesn't have that far to drop out as it clears relatively quickly and it is aided by the pressure in the bottle, you can help the whole process by chilling the primary to cellar temp once fermentation is finished, leave it there for a couple of days then chill it down as far as you can to bottle. This will help the yeast drop out and help retain the natural carbonation from the primary.
Gelatine is said to work like isinglass, it is positively charged, it attracts the negatively charged yeast and drags it out of suspension.
I have heard it said that it will remove a protein haze although protein is positively charged. In practice i've never known gelatine to remove a chill/protein haze, personally I think it is a myth.