Pay per click marketing is the process of bidding a placement on the "sponsored listing" section on a search engine.  At this time, Google and Yahoo provide pay per click advertising.  It is really a rather flexible way of advertising.  You can customize the spending to your budget.  For example, you can choose to spend as little as $50 per month if you would like to. 

To get listed in the sponsored listings, just sign up for a pay per click account through Google or Yahoo (overture).  Then bid your placement in the listings.  You are bidding for a higher, more prominent position in the sponsored listings.