what is the symbol that looks like space, but not a space? (not a  )

Question

I'm talking NOT about   but about another symbol " " that looks like " " even in text area, but that's another symbol (splitting the string by space symbol does NOT split "hello world" into two words).

Answer 1

  or one of those below maybe?

http://www.w3.org/TR/html4/sgml/entities.html

<!-- General Punctuation -->
<!ENTITY ensp    CDATA "&#8194;" -- en space, U+2002 ISOpub -->
<!ENTITY emsp    CDATA "&#8195;" -- em space, U+2003 ISOpub -->
<!ENTITY thinsp  CDATA "&#8201;" -- thin space, U+2009 ISOpub -->