Many various techniques exists, some people drop after fermentation is over and before bottling, and yet some simply cold-drop the kegs already filled with the beer for about a week, before serving, I will explain both.
Most home-brewed beer is left in a lot of its natural state, most people don’t use filters for example, there are debates over its pros and cons. If you don’t filter your beer, there is always going to be a small amount of yeast and other floaters that will make it out of the fermentor and into kegs or bottles (if you bottle).
Even when you can’t see it, yeast is suspended in the beer and it does affect its look, color, taste and overall body of the beer. So what a lot of people do, is take the keg and cold-drop it, or simply put, put it into a fridge (whatever setup) as cold as possible, but still above freezing and leave the keg there for about a week.
All the yeast and other floaters that are suspended in the beer will fall to the bottom of the keg, a thin layer will form at the bottom (not in any way bad), so then all the beer that comes out will be nice and clean, crisp, nice color, taste, and everything will improve SUBSTANTIALLY.
If you were to split a batch of beer into two kegs, and cold-drop one and not the other, you would see and experience the differences, if you want to do a comparison.
If you don’t employ a cold-drop and simply put the keg into the keggenator fridge, it too will help, the cold temperature will basically do the same thing, but will take a little longer, so don’t worry if you can’t get it to almost freezing.
Some people apply this technique to the fermentor after the fermentation is done and over with, for about a week, so then when the beer is transferred to the kegs or however bottled, there too you will gain a lot of benefit.