How do external links help SEO?
Starting at the beginning because without search engines there would be no SEO. Google was founded by two Stanford University students in 1996 as part of a doctoral research project by Larry Page and Sergey Brin. The hypothesis for their search engine was derived from the process of academic research. In order to come to a conclusion you would first have to research and cite other academic research to build upon and support your theory. Any book you open and any piece of published writing will have a list of references that were key to that theory being advanced.
Page and Brin took the idea of referencing and went about creating a search engine that could “organise the world’s information and make it universally accessible and useful”, and so Google was born. They believed the best way to establish which websites contained the most relevant information was to index the entire web and establish who links to each other. In other words the websites with the most references (links) from other highly relevant websites must return the relevant results for the user.
This is an incredibly simplistic overview of how Google’s algorithm actually works, however it is this basic foundation that has separated Google from its competitors making it the prefered search engine of over 60% of the population. As users do you need to know the technicalities of how a search engine works, I don’t think you do. As a business owner who is interested in having a website, without a basis understanding of how search engines work and without using this knowledge to make the most of SEO techniques you will be the desert in the oasis of opportunity! 
