A screen reader is a TSR. This means it will stay loaded in the background to make your normal applications talk. The actual sound comes from your sound card through either the speakers or headphones. This is a step forward from the separate synthesizers that used to be needed. The screen reader is able to determine what needs to be spoken as it appears on the screen and it gives you several ways to have the information spoken back to you as you type. You may hear either full words when you press the space bar or every letter you type. The screen reader will work better with some programs than others. It will depend on how close the program follows certain standards. Also screen readers come with scripting for programs that are widely used like MS Word and Internet Explorer. These programs will work almost flawlessly.