What is difference between de-indexing and penalizing of website by Google ?
de-indexing: In case of de-indexing google think that available content is not more good and completely useless, then google de-index your web page.
penalizing: In case of penalizing website, first you page or domain not be de-index but your domain will be fall down in ranking and domain name related other backlinks will comes on top.
DE-Indexing is fault and it no available for search engine indexed .due to spammy links ,guest posting ,clocking ,doorway pages and spammy content .
If you not follow the guidelines of search engine they will remove from their index server completely up to your website follow Guidelines