What is the use of key board button Scroll Lock?

The Scroll Lock key was meant to lock all scrolling techniques, and is a remnant from the original IBM PC keyboard, though it is not used by most modern-day software. In the original design, Scroll Lock was intended to modify the behavior of the arrow keys. When the Scroll Lock mode was on, the arrow keys would scroll the contents of a text window instead of moving the cursor. In this usage, Scroll Lock is a toggling lock key like Num Lock or Caps Lock, which have a state that persists after the key is released. (copied and pasted from wikipedia)

ScrLk (ou Scroll Lock)

Na maioria dos programas, o pressionamento de Scroll Lock não tem efeito algum. Em alguns programas, o pressionamento de Scroll Lock altera o comportamento das teclas de direção e das teclas Page Up e Page Down, fazendo com que o documento role sem alterar a posição do cursor ou da seleção. Seu teclado deve ter uma luz indicando se Scroll Lock está ligado.