Do i need to use priming sugar?

I'm new to the home brewing world and I was just wondering if I need to use priming sugar for every batch or not? The recipes I've been using have been partial mash and they don't call for priming sugar but I see a lot of stuff online that talks about using it. Is it really important to add to my beer or is it just in certain cases, and if I do need to use it at what point do I add it? Any help would be greatly appreciated...thanks. 

If you are bottling your beer, then yes. Properly fermented beer has had all the fermentable sugars consumed, and therefore there is nothing left to produce your carbonation.

Having said that (and I will probably take some heat on this) I have produced some mighty good beers by bottling BEFORE it is done fermenting, (this ususally means you have to make a bigger beer) allowing the remaining unfermented sugars in the beer to naturally ferment due to the "capped" condition where no CO2 that is produced can escape. Thus carbonation. 

But, the NORM, and the only way to get consistent results when bottling is to prime.

Anything can work from time to time but bottling prior to the completion of fermentation is a recipe for bottle-bombs!