A function key is a key on a computer or terminal keyboard which can be programmed so as to cause an operating system command interpreter or application program to perform certain actions, a form of soft key. On some keyboards/computers, function keys may have default actions, accessible on power-on.
Surge definition, a strong, wavelike, forward movement, rush, or sweep: the onward surge of an angry mob. See more.
Storm Surge is the common name for what meteorologists and call Meteorological Residual. Source: http://www.nhc.noaa.gov/HAW2/english/surge/surge_big.jpg. This illustration shows a visual breakdown of the factors affecting a surge event. Source: http://geology.com/articles/storm-surge.shtml.