They're mathematical symbols. I guess they're for situations where, say, a double-struck letter has a different meaning to the regular letter. http://en.wikipe

They're mathematical symbols. I guess they're for situations where, say, a double-struck letter has a different meaning to the regular letter. http://en.wikipedia.org/wiki/Mathematical_Alphanumeric_Symbols http://en.wikipedia.org/wiki/Mathematical_Alphanumeric_Symbo...