PPC, or pay per click, is a bidding system of advertisement for businesses to display their ads for certain searches. The most common form of PPC advertising is Google AdWords.
Imagine doing a Google search. At the top of your results, there are links at the top of the page that have a little green box that says AD next to them. These usually are directly related to the search term a user just entered. These links are companies taking advantage of pay per click advertising to draw new customers to their websites.
With PPC, you can have your site appearing at the top of the results page when people search for keywords related to your business, even in a competitive market.