The top row of keys beginning with "F" on a keyboard are known as function keys. Function keys perform different tasks in different programs, but the tasks are typically similar across programs. For example, the "F1" key will open the help file for almost any computer program, but it is up to the program's developer to program it to do so.
In most programs, pressing "F6" will move the computer's cursor, or text input indicator, to a different part of the program. Unlike the "Tab" key, which moves the cursor to the next selectable component, the "F6" key typically moves the cursor to another part of the current program window. For example, in most Web browsers the "F6" key will move your cursor from a component on a Web page to the browser's address bar or vice versa.
The "F6" key can also be combined with modifier keys such as "Shift," "Alt" or "Ctrl." When used in conjunction with the "Shift" key, "F6" will typically move the cursor through the part of a program's window in the opposite order. In some programs, such as Microsoft Word, holding "Ctrl" or "Alt" while pressing "F6" will cycle through all of the separate windows that are currently open for the program. Holding "Shift" along with "Ctrl" or "Alt" and "F6" will cycle through the open windows in the opposite order.
Most laptops assign a secondary function to their function keys to give the user a greater level of control over the laptop's hardware. The secondary functions vary widely by computer manufacturer, but are usually depicted by a small icon below the button's main label. The "F6" button on a laptop may alter the laptop's volume, change the current display or put the laptop to sleep. Most laptop's require you to hold a "Fn" button to activate the function button's secondary function. The "Fn" button is typically found near the computer's "Ctrl" and "Alt" keys.
Mac laptops' function keys function in the opposite manner. By default, the function keys perform a hardware-related function and you need to hold the "Fn" key to cause the function key to perform a software function. MacBooks made after 2007 and MacBook Pros made after 2008 use the "F6" key to increase the backlit keyboard's brightness level, if the computer is equipped with a backlit keyboard. Holding the "Option" button while pressing "F6" opens the computer's keyboard preferences window.