Note: You are currently viewing documentation for Moodle 3.2. Up-to-date documentation for the latest stable version of Moodle is probably available here: Unicode.
Unicode is a characterset that allows one to support practically any language and many special characters used in science, math and technology. Moodle transformed (1.6 or 1.7?) to Unicode to better be able to support different languages.
[| Free Online Unicode Character Map] gives you the possibility to see the different characters that are supported (or NOT!) in your browser and see which code is used if you need that. A nice feature with the characters is that you can easily enlarge the text in your browser to see them better. ([Ctrl]+[+] in Mozilla) If you are interested in Math symbols check list "22 Matematical Operators". For Chemists looking for arrows, list "21" might be interesting.
Moodle has good support for mathematical expressions in its TeX filter, but using Unicode instead can sometimes be good. In some places (i.e. CLOZE questions) the \ characters for TeX can cause problems, whereas Unicode characters won't. A user can enlage an expression with Unicode.