Cart66 Pro allows you to create a hyperlink which can be emailed to clients or used in conjunction with discounts in newsletters.
Here is a summary of what all the pieces mean:
The page you want your customer to be on after they click your link (Required)
This tells Cart66 that the link is going to add a product to the cart (Required)
This is the ID of the product that will be added to the cart (Required)
The promotion code for the promotion you would like to have applied (Optional)
Product Types, Checkout Variations:
Add to cart instead of sending customer to checkout