Backlinks are the links of your website which are placed on other websites. If your website URL is added on another website and people are coming to your site through that link then that website added to your Backlinks directory. You can check your backlinks directory on Alexa. The Backlinks cause to improve your site popularity.

To increase your backlinks, you can submitt your URL to the webiste's directory site. Another method to get backlinks is to add your site in those site which shows the worth, stats and income of websites. Simply when you entered your website one of those site, you get the details, if you are checking regularly, then that website will be added to your Backlink directory. Similarly you can get from different worth checking websites.

Another method is to add different images on your website, (if you have hosted domain) when people get the link location of image and add it to their website, then because of that image, you have also get the backlink from that website.

When you have got high rank then you do not need to work to get backlinks, but you will get backlinks automatically because of popularity of your websites e.g. someone may provide reference of your site for any posts of your site.

You can also make a page/gadget for backlinks with javascript/html coding of image and url of your site having some description.