WHAT IS "PIXEL BINNING", and WHY YOU CARE
Pixel Binning is a collection of techniques for combining multiple (nearby) pixels into a single "super pixel." This results in a pixel that, in effect, derives from the light input of a larger pixel. What this accomplishes, in effect, is pixels whose each individual size (area) is closer to the size of a much larger camera sensor. For example, a smartphone sensor that simulates the larger pixels found in DSLR cameras. However, the trade-off is that a 12.4 megapixel sensor on a smartphone that combines 4 native pixels into a single super-pixel now has a resolution closer to 3.1 megapixels (1/4th of 12.4). (If that's all the explanation you want, then check toward the end of this post for why you even care about all this...and I think you would!)
There are many variations of how to select which 4 (or 2 or 6 or any number of) pixels to combine into a super pixel. In the diagram above, the red pixels on the outer corners of a 3x3-pixel grid are combined into one quadrupal-sized super pixel. Some of these algorithms can beneficially reduce some of the random color-dots of noise characteristic in pushing small sensors to handle lower luminance (night, indoor) scenes. However, new noise artifacts can result from some of these combinatorial algorithms. Many scientists have investigated methods for pixel selection, combining into super pixels, and even post processing in specialized editors/filters. Kodak's Pixelux is one such approach.
Why do we care? It re-teaches us something that is counter-intuitive to most photographers, yet it's quite important on a very practical level of selecting our next camera.
In the ad-driven marketing arms race among smartphone camera producers, the total megapixels of a given phone's camera has emerged as the defacto popular bragging point. But, just imagine, subdividing that teeny little sensor that already is divided into 12,000,000 (12megapixels), or even 24mp, then the ad guys tell the phone-design engineers: "Hey, guys, you gotta give us a phone with a 30mp(!) camera, so our ad's can beat all the other phone producers....Maybe even up our DxO score a notch."
Frankly, I would much rather have a smartphone camera that has the option to shoot great 4mp night shots natively, rather than a 16mp camera that works best only in bright daylight.
So, you see, we really do care what pixel-binning is, and now it's clear why it's important to us. And that's not just some abstract dream, because next month LG will be releasing their new LG V30S and LG V30s phones with (get this...) a Bright Mode that shoots real nice night photos at 4 megapixel "pixel-bin" enhanced alternatives to its regular 16 megapixel camera.