What are these 𝖬𝖠𝖳𝖧𝖤𝖬𝖠𝖳𝖨𝖢𝖠𝖫 characters, and how can I use them?

Not sure when this feature popped up.. but in the "Special Characters" menu, ^SPACE (aka my _favorite place_), there are a whole slew of "Mathematical Letters". I can't even find them under the symbols list.. aka • Arrows, • Punctuation... but they're in there.. and they are CHIC! 𝘗𝘈𝘙𝘛 𝘖𝘍 𝗔𝖳𝖮𝗭.𝖥𝖱𝖠𝖬𝖤𝖶𝖮𝖱𝖪 © 𝟮𝟬𝟭𝟯 𝖠𝖫𝖤𝖷 𝖦𝖱𝖠𝖸 𝗀𝗂𝗍𝗁𝗎𝖻.𝖼𝗈𝗆/𝗺𝗿𝗮𝗹𝗲𝘅𝗴𝗿𝗮𝘆 here is a snapshot of what the above text looks like on my computer... does it look the same to everyone else? here they are in context... How can I **use** these fonts... or just type these characters directly, without having to hunt and peck with the mouse in the "Special" characters palette? EDIT: After some recent futzing with my FontExplorer Pro setup, I realized i NO LONGER HAD these beautiful fonts. After much messing around, I figured out THESE ARE NOT PART OF MAC OS X, unfortunately. They are part of the "XITS Math" font collection. This is listed as the font's "description"... > Arie de Ruiter, who in 1995 was Head of Information Technology Development at Elsevier Science, made a proposal to the STI Pub group, an informal group of publishers consisting of representatives from the American Chemical Society (ACS), American Institute of Physics (AIP), American Mathematical Society (AMS), American Physical Society (APS), Elsevier, and Institute of Electrical and Electronics Engineers (IEEE). De Ruiter encouraged the members to consider development of a series of Web fonts, which he proposed should be called the Scientific and Technical Information eXchange, or STIX, Fonts. All STI Pub member organizations enthusiastically endorsed this proposal, and the STI Pub group agreed to embark on what has become a twelve-year project. The goal of the project was to identify all alphabetic, symbolic, and other special characters used in any facet of scientific publishing and to create a set of Unicode-based fonts that would be distributed free to every scientist, student, and other interested party worldwide. The fonts would be consistent with the emerging Unicode standard, and would permit universal representation of every character. With the release of the STIX fonts, de Ruiter's vision has been realized. What a weird.. *and fabulous* font. More info can be found here.