Solr cache statistics explanation

[Marshall Gunter]

Can someone point me to an in depth explanation of the Solr cache 
statistics? I'm having a hard time finding it online. Specifically, I'm 
interested in these fields that are listed on the Solr admin statistics 
pages in the cache section:

lookups
hits
hitratio
inserts
evictions
size
cumulative_lookups
cumulative_hits
cumulative_hitratio
cumulative_inserts
cumulative_evictions
--
Marshall Gunter