Most of the documentation provided for Mathematica is concerned with explaining what Mathematica does, not how it does it. But the purpose of this is to say at least a little ...

Sqrt[z] or Sqrt[z] gives the square root of z.

DigitCount[n, b, d] gives the number of d digits in the base-b representation of n. DigitCount[n, b] gives a list of the numbers of 1, 2, ..., b - 1, 0 digits in the base-b ...

EndDialogPacket[integer] is a MathLink packet indicating the end of the Dialog subsession referenced by integer.

StreamPosition[stream] returns an integer that specifies the position of the current point in an open stream.

SyntaxPacket[integer] is a MathLink packet where integer indicates the position at which a syntax error was detected in the input line.

ApartSquareFree[expr] rewrites a rational expression as a sum of terms whose denominators are powers of square-free polynomials. ApartSquareFree[expr, var] treats all ...

ParallelTry[f, {arg_1, arg_2, ...}] evaluates f[arg_i] in parallel, returning the first result received.ParallelTry[f, {arg_1, arg_2, ...}, k] returns a list of the first k ...

PartitionsP[n] gives the number p (n) of unrestricted partitions of the integer n.

Here is a typical palette of modifiers. Mathematica allows you to use any expression as a subscript. Unless you specifically tell it otherwise, Mathematica will interpret a ...