On this website it says:
[[:blank:]] space and tab characters [[:space:]] whitespace characters
What's the difference between space and tab characters and whitespace characters? To me, they almost seem the same.
[[:space:]] class is a superset of
[[:blank:]] which additionally (apart from the space and tab of
\n, line feed on Unix, ASCII code 10),
\v, ASCII code 11),
\f, ASCII code 12), and
\r, ASCII code 13).
... in the POSIX locale, that is. Other locales may have additional space characters.