An inbound link (also known as a backlink or external link) is a link coming from another website to your own. Inbound links are important because Google sees inbound links as a recommendation of your site from. Infact, the quality and quantity of links to your site defines the Page Rank of your website (a score between 0 and 10 that Google uses to measure the importance of a website).
Inbound links can occur naturally if your website contains information that is useful, informative etc. Additionally you can encourage natural link building through link baiting, article submission, directory submission and reciprocal linking (and many other techniques!).
