Link building is the ongoing process of earning hyperlinks from other websites back to yours. Each relevant, high-quality backlink acts as a signal of trust — search engines interpret it as evidence that other sites consider your content valuable enough to reference.
Not every link carries equal weight. A link's value depends on the linking site's own authority, its topical relevance to your content, and whether it looks earned rather than manipulated. A strategy built entirely around one tactic — buying links, mass guest post networks, automated directory submissions — tends to produce a link profile that looks exactly like what it is, which is a real risk with modern algorithm updates.