Inbound links or “backlinks” (links pointing to your website from another one) can have great benefit in terms of both ranking AND indexing of your site. For instance, more links pointing to you emanating from a site that also has a lot of links will contribute to your site’s PageRank (A page that is linked to by many pages with high PageRank receives a high rank itself). This will sometimes aid the website in ranking higher for particular keywords. Also, the PageRank number (a scale of 0-10) is proportional to the amount of pages Google decides to crawl and then index. The benefits are really two fold.
Getting backlinks is not that easy, however. You must be proactive and attempt to garner new linking opportunities as often as possible. Granted, the better the content on the site, the more people who will want to naturally link to you, but that is only two thirds of the battle. Having a great website with great content does not mean that you will move from position 30 to position number 1 without getting your name out there and alerting other webmasters to your presence.
You also need specific types of links. The general consensus used to be that any link from a “.edu” or a “.gov” domain will automatically award your site great rankings, but the Google algorithm is savvy to this and Google is now specifically looking at the relevance of the website linking to you and how much of a “hub” site or authority it really is.