The main goal of an infomercial is to sell you a product or service by demonstrating and portraying it in a positive light that makes you feel like you can't live without it! The actual word "Infomercial" is a combination of the word "information" and "commercial". The content presented in an infomercial is geared to show that product/service in a positive light and inspire viewers to make a purchase. Most of the time infomercials provide an 800 number to call during the programming to make the purchase or else their website so a viewer can buy the item they want while watching the programming.
Many infomercials are formatted in a way to represent typical television programming. The goal is to keep viewers interested and watching the infomercial. Some of the infomercials may mimic talk shows so viewers don't feel like they are watching a half hour advertisement, but rather watching a show about a product or service. It's all about perception and what format will keep viewers tuned in. Interestingly enough, there are even a few infomercials that have a story line and these are often referred to as "storymercials." The vast majority of infomercials, however, are formatted based on the product, presenters, and the method that will work the best. Overall, the goal is to create a story line about the product or service offered that will capture the attention of the viewer.
The infomercial is included in direct response television and marketing because they are designed in a way to garner a quantifiable response. As a result, within a longer infomercial you will usually be able to find two to four shorter "commercials" that range from 30 seconds to 120 seconds and these are the call to action so the consumer will pick up the phone or open his computer and visit the website.
Catch phrases and repeating the same idea over and over again is a popular way for infomercials to increase their sales. It's common for the phrase "Not available in stores" to be heard by viewers so that they will be motivated to make a purchase right away.