Customers who have an account on your webstore are able to make wishlists for items they wish to purchase in the future.
You can also access this on an individual basis by going to a customer card by navigating to Customers > View customers & prospects > Click on a customer you wish to view. At the top right hand corner, click on the History button and click on the wish list.
Customers can access their wish lists in the future on the webstore by going to their My Account section and selecting My Wishlists.
Options for wishlists are available by navigating to Setup & Tools > Web Store tab > Webstore Settings and scrolling down to Customer Wishlist Settings.