The following characters play a special role in LaTeX and are called "special printing characters", or simply "special characters".
# $ % & ~ _ ^ \ { }
Whenever you put one of these special characters into your file, you are
doing something special. If you simply want the character to be printed
just as any other letter, include a \ in front of the character.
For example, \$ will produce $ in your output.
The exception to the rule is the \ itself because \\ has
its own special meaning. A \ is produced by typing
$\backslash$ in your file.