Quote from the movie Garfield: "Maybe I'll get a CAT scan."
The advertisement must create enough awareness for a possible client to start a process that would result in a purchase.
So what would be some basic ingredients for an advertisement?
Appeal, radio, TV and printed commercials need to have enough appeal to capture and hold the interest. Only when the targeted audience is 'listening' a message can be relayed. Depending on your product and marketing approach the content can be informative, funny, surprising, etc.
Recognition: The message have an unique factor that will linked it to back to you. In a campaign with multiple commercials a linking factor could be the phrase, actor(s), an image, etc.
Call to action: When your target audience views an commercial advertisement the sale of the product is not magically made. If it is a product that is easily obtainable, for instance in a supermarket, just creating awareness might be enough. Usually you will need to provide means for the customer to obtain your product or service. Advertisements years ago had a cut-out section that was a order form, or a means to get more information. Nowadays with the internet, this section has been replaced with a link to a website, email address, etc.
Technologies like QR Codes, AR and NFC can be used to have an easier access to you 'call to action', and provide a means to keep track of your advertisements success.