patt /; test is a pattern which matches only if the evaluation of test yields True. lhs :> rhs /; test represents a rule which applies only if the evaluation of test yields ...
DateTicksFormat is an option for DateListPlot which specifies how date tick labels should be formatted.
DigitBlock is an option for NumberForm and related functions that specifies the maximum length of blocks of digits between breaks.
EdgeLabelStyle is an option and property for Graph and related functions that specifies the style to use for edge labels.
FractionBoxOptions -> {opt_1 -> val_1, opt_2 -> val_2, ...} is an option for cells that specifies settings for FractionBox objects within the cell.
FrontEndEventActions is an option for the notebook front end that gives a list of actions to perform when specified user-interface events occur.
FrontEndToken["cmd"] is an object which represents a front end command token, typically corresponding to a front end menu item, to be executed by FrontEndExecute. ...
InputNotebook[] gives the current notebook into which keyboard input in the front end will be directed.
LightingAngle is an option for ReliefPlot and related functions that specifies the angle from which simulated illumination is taken to come.
LinebreakAdjustments is an option for selections that sets parameters used for calculating where automatic line breaks should be inserted.