Local SEO is a local geographic location for a city or area. If you understand basic SEO, then you know the importance of ranking in Google for specific keyword(s) or Search Phrase(s) that your customer is typing in that little search box on Google.
For example, if someone types into Google “Locksmith San Diego”, the top ranking websites for Locksmiths in San Diego would show up on page one. Apart from the Google Ads located at the top of the SERPs “Search Engine Results Page” where those businesses are paying per click, which is called PPC to get their website advertised at the top of Google. For example “Locksmith San Diego” you can see from the results below that Pop-A-Lock of San Diego are ranking on Page #1 of the search results of Google, and not paying advertising fees to do so. In fact, there are over 1,900 searches for Locksmith San Diego and it currently cost $23.17 per click (that comes out to $44k/month roughly) as of January 22nd, 2016.