Explain how caching work in Drupal?

Answer

Through caching Drupal allows to speed up website using different configuration like page caching, block caching and lifetime for cached pages.

• Page Caching:  It enables the entire HTML of each page to be stored in the database.  It reduces the amount of queries needed
• Block Caching:  You can set the cache setting for a block in views, when block created by views
• Minimum cache lifetime:  It is the amount of time before the page cache is cleared. On each cron run, page caches are cleared.
• Expiration of cached pages: It only applies for an external mechanism, for example, your browser cache or varnish