Google uses a particular search results algorithm.
Every year Google changes its algorithm 500 times each time, that is 1 to 2 times on average each day.
Once in a while, Google rolls out major algorithm updates, and when they do so, many sites suffer a drop in rankings while many others enjoy a rise in rankings.
Google Major Algorithm Updates:
Panda algorithm update lowers the rankings of low-quality websites. it is meant for stopping the sites with poor quality content and also lower their rankings.
Penguin algorithm update decrease rankings of sites that engage in black-hat SEO. This update helps in catching the sites in spamming the search results in buying links and obtaining through link networks to boost their rankings.
Google Pirate update was designed to prevent the sites with copyright infringement reports from ranking well in google search results. the majority of sites affected are relatively big and well-known websites that made pirated content such as movies, music, and books they made available to visitors for free.
Hummingbird name comes from precise and fast. It is intended to concentrate on the meaning behind the words.
It helps in increase in relevancy and knowledge graph update(Semantic search).
In the query, the entire query, the entire sentence, meaning or conversation, the Hummingbird algorithm pays more attention to each word.
Google’s Hummingbird algorithm brings better results in the application of meaning technology to billions of pages across the web, as well as knowledge graph facts in semantic search.
Google Pigeon algorithm update provides user-based local search results that are more useful, relevant, and accurate. This algorithm improves the distance and location factors in ranking the results.
Mobile Friendly Update(2015):
Google Mobile-Friendly Update ensures optimized pages for mobile devices to the rank top of the mobile search. This algorithm does not affect desktop searches. Mobile Friendliness is the page-level factor that means of the one page of your website is mobile friendly and up-ranked.