When we speak about authority in the context of information literacy and research, we are talking about cognitive authority, which is how we decide whose voices to trust in research. This is different from political authority, which describes power dynamics (such as the authority of the government to pass and enforce laws on citizens).
Authority is contextual. Different types of authority are valued in different contexts. If you're trying to choose a restaurant to eat at on vacation, you might trust the authority of reviews on a site like Yelp over that of a highly respected food scientist who has never visited the restaurant in question. If you're writing a research paper on student activists in the 1960s, you might trust the authority of someone who was a student activist, even if they don't have any scholarly credentials; but you'd also probably trust a historian who has published frequently and deemed influential by other scholars in the field, even if they were never a student activist. The point is that different people have different sorts of authority, and someone who has a lot of authority in one context may have very little in another context.
Authority is constructed. Different communities, fields, and disciplines have different conceptions of what makes a person an authority on something. Academic researchers studying the effects of sugar on human health will probably trust research from other academic researchers more than they'd trust research produced by a sugar industry group. It is important to read varying perspectives and carefully consider the authority of each. Sometimes the most prominent voices are not the most authoritative.
When researching online, it's easy to become overwhelmed by the sheer volume of information available and simply use the first few pages that superficially seem official and relevant. However, with these simple tips, you can SIFT through the sources you find to determine which ones really are best, regardless of what PageRank, social media likes, or anyone else says.
SIFT is a helpful acronym for initially evaluating source credibility. SIFT stands for:
Later, when you determine that the site is worth your time, you can analyze the source's content more carefully.