Facebook advertising is becoming known as one of the cheapest way to advertise online, undercutting the likes of Google ads and traditional web ads. Not only that, but Facebook also allows you to be much more targeted with advertising, precisely taking aim at your target market, making it more effective than other methods of online advertising.
The main difference between Facebook ads and Google ads is that on Facebook, you are trying to FISH for customers. On Google, customers are mainly looking for your service.