Mathematica normally makes as few assumptions as possible about the objects you ask it to manipulate. This means that the results it gives are as general as possible. But ...

The names of built-in functions follow some general guidelines. The main expression or object on which a built-in function acts is usually given as the first argument to the ...

ImageData[image] gives the array of pixel values in image.ImageData[image, " type"] gives the array of pixel values converted to the specified type.

AtomQ[expr] yields True if expr is an expression which cannot be divided into subexpressions, and yields False otherwise.

EdgeCoverQ[g, elist] yields True if the edge list elist is an edge cover of the graph g and False otherwise.

Mouseover[expr, over] represents an object that displays as over when the mouse pointer is over it, and as expr otherwise.

ObservableDecomposition[ss] yields the observable decomposition of the StateSpaceModel object ss. The result is a list {s_o, ss_o} where s_o is the transformation matrix and ...

VertexShapeFunction is an option and property for Graph and related functions that specifies a function to use to generate primitives for rendering each vertex.

CCS["name"] represents a Windows Compute Cluster Server with the specified name.

HPC["name"] represents a Windows High Performance Computing Server with the specified name.