Filters became popular, back in the olden days of camera phones, as a way to make bad photos look less bad.
Photos for OS X brings the same kind of damage control to the Mac. Whether it's by adding a color overlay, boosting or flattening contrast, it lets you take pictures that look wrong and make them look artistic instead. They're the same subtle filters Apple introduced for the iPhone and iPad in iOS 7 so, while they may not have the same punch as some others, they're consistent and even more importantly ?*they're non-destructive. That means you can change your mind and even revert to normal at any time.
Full story from the iMore Blog...