Reverse Proxy (Web Reverse Proxy) and Caching are two different technologies that often come in tandem, especially in DDoS.
The reverse proxy acts as an effective DDoS layer, as it is located between the attacker and the targeted server. Virtually all the network attacks directed at the server will hit a wall when they reach the reverse proxy.
Caching is a technology that resides on top of a reverse proxy. Caching stores web pages on the proxy. Under a DDoS attack, numerous requests to a single resource will result in only a single request to the server; the server will not experience the impact of the attack.
When the technologies are combined, they block virtually all the network attacks, application attacks to static pages, and, partially, other types of attacks. This technology combination is considered one of the most effective methods against DDoS.
Related entries: Web Reverse Proxy