backlinks are just like votes for Google. Thus, in case you have a website www.example.com and you have some 100,000 backlinks to your website, then Google will consider your website as a real nice website.. with 1000 votes. This will mean that the keywords you are targeting like Example, Example 101 etc, will shoot up in the result pages. Now, backlinks are two types: dofollow and nofollow. In simpler terms, Google considers only dofollow backlinks as votes. Nofollow backlinks are, well, bogus votes! Google doesn't consider as worthy. Thus, while building links (or outsourcing them) always look for dofollow links. and, there is a very simple strategy to check them as well.. i can share incase anyone is interested!