I’ll add another explanation for bitrate that I find understandable: You can think of resolution as basically the max quality of a display, no matter the bitrate, you can’t display more information/pixwls than the screen possess. Bitrate, on the other hand, represents how much information you are receiving from e.g. Netflix. If you didn’t use any compression, in HDR each pixel would require 30 bits, or 3.75 bytes of data. A 4k screen has 8 million pixels. An HDR stream running at 60 fps would require about 1.7GB/s of download wihout any compression. Bitrate is basically the measure of that, how much we’ve managed to compress that data flow. There are many ways you can achieve this compression, and a lot of it relates to how individual codecs work, but put simply, one of the many methods effectively involves grouping pixels into larger blocks (e.g. 32x32 pixels) and saying they all have the same colour. As a result, at low bitrates you’ll start to see blocking and other visual artifacts that significantly degrade the viewing experience.

As a side note, one cool thing that codecs do (not sure if literally all of them do it, but I think most by far), is that not each frame is encoded in its entirety. You have, I, P and B frames. I frames (also known as keyframes) are a full frame, they’re fully defined and are basically like a picture. P frames don’t define every pixel, instead they define the difference between their frame and the previous frame, e.g. that the pixel at x: 210 y: 925 changed from red to orange. B frames do the same, but they use both previous and future frames for reference. That’s why you might sometimes notice that in a stream, even when the quality isn’t changing, every couple of seconds the picture will become really clear, before gradually degrading in quality, and then suddenly jumping up in quality again.