Polipo is a small and fast caching web proxy (a web cache, an HTTP proxy, a proxy server). While Polipo was designed to be used by one person or a small group of people, there is nothing that prevents it from being used by a larger group.
In short, Polipo uses a plethora of techniques to make web browsing (seem) faster.
By virtue of being a (mostly) compliant HTTP/1.1 proxy, Polipo has all the uses of traditional web proxies. It is typically used as a web proxy for a single computer or a small network, although there's no fundamental reason why it shouldn't be used by a larger one.