Manual:$wgParserCacheType

Note
For a very large wiki (tens of thousands of pages) value of CACHE_DB might be preferable to CACHE_MEMCACHED. Although memcached is faster, it won't be able to cache everything (no reasonable amount of memory would be enough), while DB will be. Therefore DB will have much higher percentage of cache hits.

If you set  then the values for $wgParserCacheType and  will inherit it. You do not need to set those variables unless you plan on doing something very advanced.