What is pay-per-click advertising?
An alternative and/or supplement to search engine optimization, pay-per-click (PPC) allows you to pay for a top search engine ranking for desired keyword(s). Advertisers (i.e., website/business owners) bid for the top ranking for a given keyword.
The advertiser with the highest bid secures the top ranking for that keyword, until he/she is outbid. The second-highest bid secures the number 2 ranking, the third-highest bid will claim the 3rd spot, and so forth.