Quotes are used when assigning values containing whitespace or special characters, to delimit variables, and to assign command output. They also improve readability by separating arguments from commands.
|'...'||remove the special meaning of enclosed characters except '|
|"..."||remove the special meaning of enclosed characters except $, ', and \|
|\c||remove the special meaning of character c|
|`command `||replace with the standard output of command|