Audacity is like Paint for sound: You can play with individual pixels/samples, and use basic functions like rectangles/reverbs, but that’s about it.
Ableton is like Photoshop for sound: You need to write custom plugins to play with the pixels/samples exactly how you’d like, but you don’t need that anyway because you have so many shiny tools and functions, like automation/gradient fills and a huge choice in effects/filters.
ANALOGIES YAY! Disclaimer: I’m probably a little sleep deprived, so I may or may not regret posting this. My judgements should probably not be trusted completely. Haha.