To translate characters to and from their HTML entities.
åäö -> HTML - translates characters to HTML entities.
HTML -> åäö - translates HTML entities to characters.
The characters which are translated are all you find in the "small chars" and "capital chars" menus (except eth, thorn and y´) plus the Spanish ¡ and ¿.
If some text is selected, the characters are translated within the selection, otherwise they are translated in the whole document.