Some characters and words have special meanings to the shell. The quoting process is used to remove these special properties.
There are three ways to quote special values
The escape character (\)
Single quotation marks (')
Double quotation marks (")
The escape character, a backslash \, causes the shell to ignore the special properties of the following character.
Single quotes around characters stop any special meanings. Strings escaped with single quotes may not contain a single quote because the escape character has no effect within single quotes.
Double quotes preserve all characters within them except $, ' and \. The escape character only works for a limited number of characters within double quotes, these are $, ', " and \.