It's imperative to know about link building while dealing with SEO campaign. One of the SEO tactics that any webmaster can perceive to promote the site online is to establish maximum "high quality links" for the website.
"Link building is the technique to develop "inbound links" to your website for increasing the web traffic and elevate your Rank in Search Engine like Google, Yahoo etc."
The Google responses to the question
"How can I improve the ranking of my website?"
as
"Generally the webmasters can enhance their ranking by increasing the number of quality sites that links to your WebPages."
In nutshell, we can say that valuable back links are considered as the web votes in Search Engine ranking formula. But this doesn't end here. There are some auxiliary considerations confronting the rank of your website. These are
Who links to your site?Where to place the link?What they say about you?Why should you link to them?Etc.
These are rather more important factors as compared to the number of sites linking to you.
Why to use back links?
Some webmasters builds back links to increase their back links, while other accomplishes it for enhancing their Page Rank etc.