Authority is the importance or weight of a domain or page relative to a given search query. Search engines want to present top results that are most likely to satisfy the user with accurate, reliable information that fully answers the intent of the question or topic.
The web is built on interconnections (hyperlinks). When external websites link to others, those links act like an endorsement (or “vote”) and suggest that the receiving website is a good resource for a given topic. In principle, the more votes a site has, the better and the more authoritative a search engine would consider it to be, ranking the site higher.
Not all links are created equal.
The goal is to receive and accumulate links from quality sites. Pages that rank well within the search engines have 100s of backlinks from other quality sites and well-chosen optimized internal links, which take users to curated content within the site. It’s important to note that acquiring backlinks takes time and should be conducted carefully. Tactics like buying backlinks or other unnatural approaches could hurt the entire site.