Unicode is a standard for representing text in just about any writing system a language uses. This might sound fancy and complicated at a user level, but it’s how we’re able to use computers in any language. Each symbol in Unicode, such as A, a, 2, or ‽, corresponds to a unique number across all computers, languages, and platforms. As an example, the interrobang’s Unicode coding is U+203D. Chances are your computer and its software already support Unicode; many modern browsers and programs come with Unicode out of the box, so you don’t have to think about Unicode on a day-to-day basis unless you really like looking at your character map. If you do, I can’t blame you. There are some cool characters there.
There’s a non-profit Unicode Consortium designed to develop and promote Unicode. A lot of work goes into making sure Unicode is consistent across all these platforms, so Unicode is indeed serious business.
If you are one of those people who has looked through the character map, you know that Unicode supports a lot of characters, more than you probably understand. It has to understand the Roman characters that I’m typing in right now, of course, but it also has to understand accented characters, Arabic characters, Cyrillic characters, Wingdings characters, and all sorts of other characters. There are also symbols for some emoticons and mathematical symbols, along with some symbols you might be surprised at.
Here’s a video of every single Unicode symbol, one per frame. It’s about half an hour long, which should give you an idea of how many characters Unicode supports.