A Search Engine is a web site that collects and organizes content from all over the internet. Those wishing to locate something would enter a query about what they'd like to find and the engine provides links to content that matches the requirement what they want. Search Engine advertising includes sponsorships, Pay-For-Placement (PFP) advertising, and sometimes maybe contextual advertising. Search Engine advertising generally follows a PFP model.
Pay and you're guaranteed top placement in a Search Engine's results both on the search site and within its distribution network as long as your ads and landing pages meet quality guidelines. As regards real estate, millions of searches are done each day on multiple Search Engines for search queries like "Sydney carpet cleaning", or "Sydney NSW carpet cleaning". The Search Engine returns results for carpet cleaning related sites and content for the Sydney, NSW area in this case. The sites are ranked by an algorithm which is highly secret and based on complex formulas. These formulas are also changed frequently by the engines.