Search engines like Google have criteria for websites in order for them to rank highly. Such as mobile responsiveness, speed, security, relevance and authority to name just a few! Essentially the better, more relevant experience a user has the more chance of a website ranking highly. 

These are the factors on your physical website that help push you up the rankings. Such as the content, the format of your content and other technical aspects that help search engines “read” and understand your website. 

These are factors outside of your site that affect your rankings. Things such as other trustworthy websites linking to your website help Google to verify if your site is worth sending users to. Beware this can also work in the opposite direction!