(Former Google Adwords) are particularly valuable because, as the most popular search engine, Google gets massive amounts of traffic and delivers the most impressions and clicks comparing with any other PPC platform.
How often your PPC ads appear depends on a number of factors, some of the most important ones are:
Web Page Quality – Creating optimized web pages with persuasive, relevant content and a clear call-to-action, tailored to specific search queries.
Quality Score – Quality Score is Google's rating of the quality and relevance of your keywords, web pages, and PPC campaigns. Advertisers with better Quality Scores get more ad clicks at lower costs.