General   (General discussion, talk about anything.)

Hi Ena,
I did a search and there are several explanations but it appears to be a replacement for as character that doesn't exist within a particular font.
The general explanation I found is this:
"The replacement character , a black diamond with a white question mark, is a symbol found in the Unicode standard at codepoint U+FFFD in the Specials table. It is used to replace an unknown or unrepresentable character, or indicate problems when a system is not able to render a stream of data to a correct symbol."
Hope this helps.