If a business provides services nationwide it may try to rank for just the keyword. If it’s a local business it would try to rank for the keyword + the geography. So for e.g., a national chain of plumbing supplies provider would want to rank for ‘plumbing supplies’, while a local store that serves just Washington DC would want to rank for ‘plumbing supplies DC’. Local SEO is intended to get customers who live in the area to support that local business.