Unicast: one IP address = one machine; all traffic goes there. Anycast: many machines share one IP; the internet's routing picks the shortest path, so each user reaches the nearest server with no central dispatcher. Benefits: lower latency, resilience (if a site drops, traffic goes to the next nearest), DDoS absorption. "Nearest" is in routing terms, not physical distance or load.
Reactive (pull): store after the first request; miss -> fetch -> keep a copy. First user is slower; only caches what is used; best for unpredictable/long-tail content. Proactive (push): predict demand and push content before it is requested (e.g. overnight); first user is fast; may cache unused data; best for predictable/scheduled content (a release, live event, big update). Edge storage is small, so the real question is what to keep.