Flush Magento cache is a procedure referred to clearing stale data in Magento cache storage. It is done at System > Configuration > Cache Management by either or by buttons:
- Flush Cache Storage (recommended and fastest): empties Magento cache storage without any checks what is stored there.
- Flush Magento Cache: every cache tag is looked up for active caches and found cache data is deleted.
The difference between Flush Cache Storage and Flush Magento Cache is simple, Flush Cache Storage just empties cache directory (or any other cache storage) without checking anything in that directory. With Flush Magento Cache any existing cache data file is searched for and only valid cache data deleted file by file, tag by tag.