Now to another really big topic, Backlinks. What are Backlinks? A "backlink" is a link from another page to yours. There is also the difference between a deep link and a "normal" link. That was a lot of technical terms, but we can't continue here without them.
Backlink vs. deep link:
Backlink = link from another website (domain) to your page
Deeplink = A backlink that does not link to your home page, but to a specific subpage.
Why are inbound links so important? Quite simply: the most important point is of course that other websites report about you, and the visitors of the other website should then come to you and continue reading on your site. This will give you additional visitors. Having lots of visitors is very good for Google and Co. and will also improve your ranking. But another important part is the following: When Google did not yet exist (yes, those times really did exist! I lived to see them!), search engines listed purely according to the number of keywords. So if one page had the keyword five times, it was displayed before the other pages that only mentioned the keyword once or twice. This meant that the Search engine optimization pretty simple. However, the users of these search engines quickly had to deal with pages that had nothing but the keyword 100 or 200 times on them, but otherwise no useful content.
Backlinks as the most important quality criterion for search engines
At the time, Google had realized that this was not the solution and was looking for a way to better assess the value of a website. The two inventors of Google had recognized that pages that were frequently linked were apparently better than others that had fewer links. So they developed a logarithm to get a PageRank (page value) to determine the order of the search results list. Thus it is clear why we Backlinks need. Even if this is no longer the decisive factor nowadays. Nevertheless, some should be created.
However, not every backlink is good for the site. I have written an article about how to get good backlinks. Backlinks gets. It also applies here, class instead of mass! Also to influence not only the linkjuice, but also to get visitors, which has become a very important point.
By 
German 
English 