Simply put SEO or search engine optimization is the art of getting Google algorithms to steal your information and display it as their own on their SERP or search engine results page. This is as much science as it is art. Not only do the algorithms evolve and change, but so too how Google displays the information. Once upon a time, being the top listing, just below the paid adverts, was a recipe for success. But with the introduction of features such as the Three Pack, People Also Ask, & Business Listings, the first link now lives well below the fold.
So while SEO may be the gift that keeps on giving, a healthy SEO strategy is designed to evolve in lockstep with improvements in the search ecosystem.