What is the purpse of <svg width="2000" height="2000">
<svg width="2000" height="2000"> <circle cx="80" cy="80" r="50" fill="green" /> </svg>
It sets the "coordinate system" that is used in the svg. Here, it means that your x values can range from 0 to 2000 and so can your y values.
Svg is the container for svg elements. Just like you use html as a container for html elements Similarly it creates a viewport where your svg elements can come into action
It sets the size of your viewport, 👑 Prometheus 🇸🇬 is right in some extend, but the fact that It has a height of 2000 pixels doesn't always mean your range is going to be from 0 to 2000, usually while working with SVG you use viewBox attribute to keep the range to a small number without changing the size of your viewport, thats because its easier to work with a range of 100 pixels width and 100 pixels height than a range of 2000 pixels width and 2000 pixels height.
If you want to understand better SVG you can check my notes, just write karak10notes.c1.biz