Caching is the way of storing db request results into file system.
Say you querying your system for popular members (orderby="totalviews", in my opinion it's more relevant to popularity than "rating").

When any site visitor visits page with {members:} call system iterates through whole db and then compares every members totalviews value and sort with it. Unlikely members rating will change drastically next 5 or even 10 minutes. So it's good way to save your server resouces by storing result of this operation for 10 minutes.
After 10 minutes system will do SELECT operation again to update results. To get this done you need to put cache_time="10" (store for 10 minutes) and cache_name="popular" - name of cache file. Basically you don't need to set cache_name param when your cache_time="0" cause no results cached (stored in filesystem).
Different cache_name for different {members:} calls (popular, new members, latest visitors) so they do not overwrite each other and you don't get women instead of just latest visitors.