She speaks from the trenches where she's been testing web-based software. You and your team are charged with testing this new beast, this web application. You've been testing enterprise applications, database applications, whatever the flavor is at your company. There is an incredible range of sophistication in web applications from a simple company website with some order fulfillment to sites like Yahoo or Amazon. One way to look at the web application architecture is to take the model of a traditional business transaction application and to replace the user front end by the website.
Mechanisms are in place to facilitate that transaction between client and company.
But instead of a sales rep, a clerk, or a cashier, you have a browser pointing at a website. Think of a vending machine. It fills orders based on input from users, verifies transfer of funds, and has a basic user interface. Now add some complexity. And to top that off, people won't be putting coins in the machine, but swiping their credit cards in a reader - so you'll need to have each transaction approved by the credit card companies.