Zen Cart Auto Add allows you to specify items to automatically add to the cart when other items are added. It's good for adding free gifts, or automatically adding Better Together or other discounted pairings.
Items which are set to Auto Add must be able to be added to the cart from a normal listing page. For example, if you search for the item, the search results page shows the item with "Add to Cart" functionality and not a "More Info..." link). What this means is:
For more information, please visit this product's webpage.