NotebookInformation[] gives a list of properties of the current evaluation notebook.NotebookInformation[notebook] gives a list of properties for the specified notebook.
Overscript[x, y] is an object that formats as OverscriptBox[x, y].
Padding
(Built-in Mathematica Symbol) Padding is an option to various array and image operations that specifies what padding to use when extending beyond the original data specified.
PassEventsUp is an option to EventHandler that specifies whether events handled by a particular event handler should be passed up to event handlers in outer expressions.
PlotStyle is an option for plotting and related functions that specifies styles in which objects are to be drawn.
PodStates is an option for WolframAlpha that determines information about the states of the pods.
PropertyList[{obj, item}] lists the properties available for item in obj.
ResumePacket[] is a MathLink packet used for synchronization with the Mathematica kernel.
Round
(Built-in Mathematica Symbol) Round[x] gives the integer closest to x. Round[x, a] rounds to the nearest multiple of a.
ScriptSizeMultipliers is an option for Style that specifies how much smaller to render each successive level of subscripts, etc.