Netscape Navigator and other newer browsers have cacheing built in. On a single-user system, such as a PC on a phone line, this may be adequate. You can tune the cache parameters to make the cache larger, or check entries more often. Even on a single system, if you use more than one browser or have more than one user, a proxy cache may help since cached documents can be shared among all agents. The real benefits accrue from using a proxy cache on a LAN with many users.
Any new page accessed by anyone is stored in the cache.
The next person to access that page gets the cached copy, at full LAN speed, rather than going to the source. This may be a thousand times faster, or more. Other browsers, such as Netscape, have a more sophisticated scheme for supporting multiple proxies. Netscape has a scheme for automated proxy handling using Javascript. Mosaic-2.7 also allows a list of proxies.