NeverSleep is a fancy app that puts an icon in the right side of your menu bar. Click it to prevent your Mac from automatically going to sleep, dimming the screen, or starting screen savers. Click it again to go back. Right-click (or ⌘-click) the icon to show the menu.
NeverSleep disables either lid and/or idle sleep on your MacBook - any MacBook - allowing you to prevent display sleep while playing movie or simply just to quickly stop the system from going to sleep on idle.