system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How do different resolutions work?

Like, say you have a 1920x1080 pixels monitor. You play a 1920x1080p youtube video. All is well. Now you want to set it to a lower resolution. The way I can think of to do that, is to take four pixels in a square and take the average colour and brightness of that pixel and make that the same for all four. Now you've devided the amount of pixels in each dimention by two, so you have 960x540, unless im making a mistake here. So ELI5 how do you get 720p resolutions and other ones, and how do they translate to physical pixels in your screen, a number that doesnt change.
gpt
Imagine a grid of ~2M cells, going 1920 across and 1080 down. Now, make a grid of ~1M cells, going 1280 across and 720 down. Then, stretch the second grid uniformly until it's the same size as the first grid. For whatever cells overlap, you take the average color.