They guarantee your site will be submitted within a limited amount of time. Examples are Altavista , Excite , Looksmart and Yahoo . Companies submit their site's descriptions and titles, along with a list of keywords to the engine. They also specify the amount of money that they're willing to spend on each keyword. Most engines specify a minimum amount of money needed for a company to open an account.
Users have to register themselves first.
Because of this registration Web marketers can focus on certain users based on keyword terms, gender, age and zip code. For example, a woman searching NetFlip for the term 'shoes' will receive different search results than a man searching for the same term. This service is getting very close to be an electronic commercial marketplace. The advantage is that every time you enter a certain shop you receive a dime.