GridBox[, , ... , , , ... , ... ] represents a two-dimensional grid of boxes or strings in input and output.
In a notebook, columns of a GridBox can be added using , and rows using (Control-Return).
, or a menu item can be used to start building a GridBox.
You can use tab to move from one entry in a GridBox to the next. moves out of the whole GridBox.
In StandardForm and InputForm, GridBox[list] is interpreted as list.
You can place parentheses around a GridBox to make it look more like a matrix, but these are by default ignored when the GridBox is interpreted.
The following options can be given:
GridBox is a low-level construct that works only for two-dimensional arrays; TableForm and MatrixForm are higher-level constructs that can also be used for higher-dimensional arrays.
In StandardForm, explicit GridBox objects are output literally. You can use DisplayForm to see the display form of such objects.
See The Mathematica Book: Section 2.8.10.
See also: TableForm, MatrixForm, RowBox, OverscriptBox, UnderscriptBox, AdjustmentBox.