if you believe your website ranking is being harmed by relevant inbound link or low-quality links points to you. In that case, use to Disavow link tool and choose those irrelevant links and submit Disavow link button. This helps to communicate to Google not to take these inbound links into account when ranking the website. Disavow link tool helps to disallow irrelevant link to the site.
Matt Cutts said repeatedly at PubCon, on the video (see Matt Cutts Video below) and in the blog post that you should try not to use it, don't use it, really. Why? One example he said is do not disavow internal links – it can hurt. Right, Google is just using this as a "hint" or "signal" now, like they did with the rel=canonical when that launched, but this will be a powerful signal within 6 months – so be careful if you have to use it.
