A string is a sequence of characters that are enclosed within a pair of double quote characters (" "). The opening double quote determines the start of the string and the closing double quote determines the end of the string.
A name can be formed by enclosing any sequence of characters in a pair of left single quotes (` `). The opening single quote determines the start of the name and the closing single quote determines the end of the name.
This error occurs when the double quotes associated with a string (or, similarly, the left single quotes associated with a name) are unclosed (for example, an opening or closing double quote is missing), or an extra double quote is inserted around the string (or an extra single quote is inserted around the name).