If you copy the contents of a StandardForm cell into another program, such as a text editor, the Wolfram System will generate a ∖!∖(…∖) form where necessary. This is done so that if you subsequently paste the form back into the Wolfram System, the original contents of the StandardForm cell will automatically be re-created. Without the ∖!, only the raw boxes corresponding to these contents would be obtained.
The Wolfram Language will usually treat a ∖(…∖) form that appears within a string just like any other sequence of characters. But by inserting a ∖! you can tell the Wolfram Language instead to treat this form like the boxes it represents. In this way you can therefore embed box structures within ordinary character strings.
|\*input||construct boxes from input|
When you type aa+bb as input to the Wolfram System, the first thing that happens is that aa, +, and bb are recognized as being separate "tokens". The same separation into tokens is done when boxes are constructed from input enclosed in ∖(…∖). However, inside the boxes each token is given as a string, rather than in its raw form.
Within ∖(…∖) sequences, you can set up certain kinds of boxes by using backslash notations such as ∖^ and ∖@. But for other kinds of boxes, you need to give ordinary Wolfram System input, prefaced by ∖*.
∖* in effect acts like an escape: it allows you to enter ordinary Wolfram Language syntax even within a ∖(…∖) sequence. Note that the input you give after a ∖* can itself in turn contain ∖(…∖) sequences.
|∖!∖(input∖)||interpret input in the current form|
|∖!∖(form∖`input∖)||interpret input using the specified form|
When you copy the contents of a cell from a notebook into a program such as a text editor, no explicit backslash backquote sequence is usually included. But if you expect to paste what you get back into a cell of a different type from the one it came from, then you will typically need to include a backslash backquote sequence in order to ensure that everything is interpreted correctly.