Cassie Evans has a great intro to motion paths. That is, being able to animate an element along a path. Not just up/down/left/right, but whatever curvy/wiggly/weird path you want.
It’s an interesting subject because there are so many different technologies helping to do it over time. SMIL, JavaScript-powered animation libraries, native JavaScript APIs, and even CSS via offset-path and friends. I think offset-path is funny – it was changed to that name from motion-path as you don’t technically have to apply motion to an element you place on a path in this way.
There’s no clear winner. I’m (perhaps obviously) a fan of doing stuff like this in CSS whenever possible, but the browser support there is essentially Chrome-only. Plus seeing SVG path values in CSS always feels a smidge uncomfortable because of the unitless numbers. SMIL feels like essentially dead technology, but at least then you’re in SVG-land and the paths make good sense in that context. If browser support is vital, you have to use a library.
I do think there is untapped cool design possibility in motion paths. It’s not just for landing space ships, but can be for practical stuff like how a modal enters a page.