Backlink (Link Building)
A backlink is an incoming link from an external website to your own site, which search engines read as a signal of trust and authority. Link building is the deliberate strategy of acquiring such backlinks in order to improve a website's visibility.
In practice
With backlinks, quality counts for considerably more than sheer quantity: a single link from a topically relevant, trustworthy site is usually worth more than many links from weak or irrelevant websites. Buying links or using so-called link farms breaches Google's guidelines and can lead to penalties. Sustainable link building happens organically instead, through content that is worth linking to on its own merits and through PR work, partnerships and mentions within the industry.