Google is going through various changes. It is trying to change the behavior of search engine and make it much favorable to the users. Before 2010, Google was not applying many measures to correct search behavior except going down heavily after paid links and very highly spammed comments but since then, it has come a long way.
In 2011 the first major update named Google Panda came into being. It completely changed the Internet because it affected lots of websites that were using spun content or content farms that were getting huge traffic by automation. After Panda, these sites were termed as spam. Content quality again became at the top of ranking your website, and Google showed the world that it still dominates in providing user-friendly searches to its users.
Panda has gone to various updates namely: Panda 1.0, Panda 2.0 and various others variants that even more enhanced the algorithm for finding bad quality content. In order to rank your website for long-term, you have to write long and high-quality content that is filled with juices of images, videos and various other types of enhancements.
After Panda came Penguin, which cracked hardly on bad quality Backlinks. It majorly focused on highly focused anchor text and bad quality link building methods like comment spamming and blasting. Just like Panda it was also quite revolutionary and made heavy changes to the ranking algorithm.
Google Hummingbird is also a recent update that focused on user experience to rank websites. However it is not clear at present, what effects it had on rankings of various websites. It is also noted that Google is manually checking the search results for highly spammed terms like payday loan et cetera. So, you won’t be able to rank on the search engines for terms like payday loan if you are building automatic backlinks or using any other black hat methods, because even if you rank, you have to face a manual review.
Most of these changes shows us that Google is more and more focusing on quality results from its index. It has already clarified that it is going to use user experience as a tool for finding out how much better and relevant content is. That being said Backlink still is the most precious thing to get you ranked, and it will surely be because there are no other good ways at least in the coming future to sort out websites.