Imagine you’re paying bills at your online banking Web site. You have to think about what bills need to be paid when, look up your balance, decide how much to pay on your credit cards, and click the right buttons to get the payments processed. As you do this task, there are things you’re thinking about and remembering (cognitive), things you’re looking at on the screen (visual), and buttons you are pressing, mouse movements, and typing (motor).
In human factors terminology, these are called loads. The theory is that there are basically three different kinds of demands or loads that you can make on a person: cognitive (including memory), visual, and motor.