What's an author's purpose?

The easy Chopper 3 will chop your vegetables for you in about 30 seconds. It is easy to use and you can use any vegetable. The cost is $29.95. Order yours today!

The author's purpose is to persuade.

Explanation:

There are three general purposes a person can have when writing or speaking: to persuade/motivate, to inform, or to entertain. Propaganda and advertising have the purpose of persuading people to do something. Usually, advertising focuses on making people buy a certain product. For that reason, they describe the product, its characteristics and features, and make it seem as if it is a nice thing to have - something that will make your life easier and happier. That is what the author does when describing the chopper. This product is fast - vegetables are cut in 30 seconds - and cheap - $29.95. At the end, we even have the use of imperative - "Order yours today!" The purpose here is clearly to persuade people to buy this product.