If there's one thing you'll be used to talking about when it comes to SEO, it's ranking. The order in which your content appears in search engines makes a huge difference to how much traffic it rakes in.
Search engines want to rank good content higher than less relevant material and spam. That way, happy searchers will come back the next time they have a query.
How does a search engine decide which pieces of content in its index are best? While the exact formula is unknown, content that is relevant to the searcher, frequently cited by other sources and which shows high engagement from its readers is generally likely to rank higher.