A popular little SVG animation technique is path drawing. If you can’t picture it, here’s a collection of a zillion examples I’ve created. Essentially the stroke around SVG shapes draws itself over time.
I think it’s easiest to think about starting with CSS, and how the dash properties work as applied to an SVG shape. How they can get longer, and even long enough to the point of covering (or not covering) the entire shape. Then offsetting them when they are that long is how the drawing works.