SEO is the work that goes into a website to make it appear higher in the results of search engines like Google and Bing. Search engines like Google look at two things when evaluating your website and deciding where to rank it – relevance and trust.
Relevance is the content of a website and the code behind the scenes. If your code is optimized and the content on your site is relevant to a search, Google will move you up in the rankings.
Trust refers to how many other sites on the internet are linking back to your site. If a large number of high-quality sites are pointing to you, Google will start to trust you and move you up in the rankings.