Local SEO are optimization strategies to place and highlight a site in local Google searches, that is, Google delivers in its search pages, for a specific user, the sites that contain a geographical component equal to the one that searched.
For example, if the user is from Lisbon, the search engine will put at the top of the search, the sites that have that same location, so the location of the user enters as an essential factor to filter and sort the results in response to what he wants.