Stacking images is an incredibly useful and powerful tool in photography. You can stack images with multiple exposure values to enhance dynamic range (HDR). You can also achieve some really unique perspectives with focus stacking. For example, you can take an image with a prominent foreground and merge multiple images to have your background and everything else in focus. This method is superior to shooting at a high F stop which can cause lens distortion. Further, cameras like the Sony A7RIII with pixel shift will let you stack images to achieve incredibly high resolutions. The applications are only limited by your imagination.
In this particular video, Nico Carver (Nebula Photos on YouTube), is using stacking in order to boost the resolution and detail in his astrophotography. By merging 1024 images of the Orion Nebula he is able to bring out the full color and detail in the dust/gas clouds while also showing us his workflow. We get to see the comparison from 1 image through to 64, 256 and all the way up to 1024. The more images are being stacked the more details become apparent in the nebula but, even more importantly, noise and unfavorable artifacts are decreased at the same time.
As a minimalist, astrophotography has always interested me but I could never justify the gear to do the art justice. Certain pieces of gear can also be prohibitively expensive (mounts) if you really want to dive deep into the style. However, the results are truly glorious and I often browse images from artists like Nico who are willing to invest in their gear, technique and have the patience to produce their epic images.
Make sure to check out his video as there is a lot to be learned. Even if astrophotography is not your goal, again, stacking images can be an invaluable tool in whatever style of photography you prefer. Likewise, make sure to check out some of his stunning images on his Instagram.