Escape

The escape character (\) is used to "escape" special characters.

Special characters are those which have a reserved meaning on UNIX like OSs.

An example is the space character. if you want access a file that has a name with a space in it you need to escape this character, to ensure that it is not treated as a seperator between file names, or between switches.

For example if you typed

emacs my file.txt

emacs would try to open the files "my" and "file.txt".

but if you escaped the space character

emacs my\ file.txt

then emacs would try to open the file "my file.txt".