When a spam trigger is set off by Google like the very large increase of backlinks to a website all of a sudden your website can be an example. Your website may become penalized automatically until a manual action is taken by one of Google’s employees where they manually check out the situation to see if the sudden increase of backlinks was purchasing them or if it is natural from a super popular article posted on your website.
A Meta Description is located in the
section of a website whose sole purpose is to describe what the web page is about. In the past, the meta description was shown in the SERPs (search engine results pages) but this was abused and Google now shows excerpts of the web page instead of the Meta Description in the SERPs most of the time instead. Although the Meta Description can still be shown in some cases. This still holds value (but very low) in Google’s search engine algorithm.
The Meta Keywords tag is located in the <header> section of a website where you used to put keyword phrases to help the search engines determine how to rank your website. Due to the abuse of using keyword stuffing and improvement of the search engines, this has absolutely no value anymore.
Meta Tags are located in the <header> section of a web page. Examples of Meta Tags are Meta Description, Meta Keywords, Meta Refresh, etc.
MFI (Mobile-First Indexing)
This is a term and action created by Google in 2018 that describes that they will index the mobile version of a website before the desktop version of a website since most searches are done on mobile phones more than desktops now.