Understand size of regio how it's work

hello dear

I need to understand how to realize content that fits with the size of the area, for example in my area I made 1913 * 818 (10,166).
If I want to have a video full region, how do I create the video.

In general the rule is to have the region and video/image in the same aspect ratio.

ie for full screen region in most common resolution 1920x1080 (16:9 aspect ratio) you would want your videos/images in 16:9 aspect ratio as well.