Why is it important to get backlinks

I am not an expert in SEO (Search Engine Optimization), but one thing I know is that if you want to get more and more visits to your blog, you have to get backlinks.
Backlinks are not only important to get a higher position in Google, they are important because every backlink you get is a door to your blog.

To clarify more what I say, think it this way, Backlinks are incoming links to a website or web page, so the number of backlinks is one indication of the popularity or importance of that website or page.
They are also important of significant personal, cultural or semantic interest: they indicate who is paying attention to that page.
However, if you want to know why they are important for SEO, I give you this description about Backlinks that I took form Wikipedia:
Search engines often use the number of backlinks that a website has as one of the most important factors for determining that website's search engine ranking.
For instance, Google's description of their PageRank system notes that they interprets a link from page A to page B as a vote, by page A, for page B.
Therefore, that is why it is important to get backlinks, not only for SEO reasons, but also for personal reasons.