SEO, also known as Search Engine Optimisation is a process used in online marketing to optimise websites in a way that is friendly to search engines. Currently, the most used search engine is Google and so SEO efforts are usually aimed at it.
The goal of an SEO campaign is to drive organic traffic to a website using optimisation techniques like creating quality content, optimising technical aspects of a website, creating relevant titles to web pages, generating backlinks that drive traffic and increase authority in the eyes of a search engine and hundreds of other factors. These techniques if executed correctly, result in positioning web pages high in search engine results page or more precisely said high in terms of relevance to the user currently searching for that query.
SEO is not be confused with paid advertising like PPC (Pay Per Click) since, in SEO, you don’t pay to have your ads or web pages displayed, you hire an SEO consultant that systematically generates traffic for you through the processes mentioned above.