system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: In Youtube, why do I see a difference between the 720p setting and the 1440p setting even though I have a 720p monitor?
gpt
Because youtube videos are heavily compressed, so the higher bitrate of the 1440p stream effectively leaves you with a *better* 720p stream once it's resized to 720p.  You'd get pretty much the same benefit if it were actually possible to get a 720p youtube stream with the bitrate of a 1440p stream.

(One note, this depends on the source material being relatively high quality.  The original recording from, say, a cell phone likely isn't to contain enough information to really benefit from a higher bitrate stream)