Shopping Carts vs. Stores is a blog entry written by James S. Huggins. James has posted this in Yahoo groups and perhaps other places. It is an astute description of the differences between Shopping Carts and Stores. It is helpful to think about when picking software in these categories.
I use this information when I talk to clients, so I am happy to give James some credit.
I add two things. I separate the checkout from the shopping cart. So in the analogy, I talk to clients about the grocery store and what the store does, the shopping cart and what the shopping cart does, and the checkout and what it does.
And just to make it more interesting, I also have girl scouts sitting outside at a table selling cookies to give a contrasting transaction. The transaction at the girl scout table blends everything into one transaction.