There are more special keys above the alphabetical keys; of these the function keys(please see next image) are used for different functions, depending on situation and the program currently being used. The manual for these functions is usually available in the manual for the program.
The bit is a basic unit of information in computing and digital communications. A bit can have only one of two values, and may therefore be physically implemented with a two-state device. These values are most commonly represented as either a 0 or 1.
The byte is a unit of digital information that most commonly consists of eight bits.