It is the character the key produces. In most cases, special keys will be named as follows: Esc, Tab, CapsLock, Shift, Control, Option, Alt, Command, Win, Return, Enter, Space, Fn, Delete, Backspace, Help, Insert, Home, PageUp, Del, End, PageDown, F1 through F15, PrintScreen, ScrollLock, Pause/Break, Clear, NumLock, KP=, KP/, KP*, KP-, KP0 through KP9, Up, Left, Down, and Right.