The usual terms are single and double quotes, or in shell scripting hard
, due to the differences in their behavior.
The way to understand it is that single quotes escape everything
up to the next single quote (like a toggle), while double quotes do the same, except that they do not
", and "\
" history expansion is also allowed in interactive sessions). This allows variable and command substitution to occur inside them, and they can still be escaped when needed.
Notice that the two quotation marks themselves are not treated specially. This means that double quotes escape single quotes, and single quotes escape double quotes. That's why pan64's solution works (the single quotes are escaped by the doubles), while the original doesn't work because backslashes don't function inside single quotes.
See the QUOTING section of the bash man page for a more detailed description.
Read these links too for more on how the shell handles arguments and whitespace: