PPC advertising is short for Pay per click advertising. i.e. each time someone clicks on one of your adverts, you have to pay, and if they don’t click on it, then there’s no cost.
You have used search engines. The results at the very top or the sponsored links in the right hand column are what people have paid for. The idea behind it, is that more people are likely to click results at the top of the page, in much the same way as people in a supermarket are more likely to buy something at the front of the till. The hope then is that these visitors will keep coming back to your site and because you are the first name they come to, yours is the one that they are more likely to remember and make a habit of visiting.