Question: Why do Unicode code points appear as **`U+`**`<codepoint>`?

For example, `U+2202` represents the character **∂**.

Why not `U-` (dash or hyphen character) or anything else?

Answer: 
It depends on what version of the Unicode standard you are talking about. From [Wikipedia](http://en.wikipedia.org/wiki/Unicode#Architecture_and_terminology):

> 
> Older versions of the standard used
>  similar notations, but with slightly
>  different rules. For example, Unicode
>  3.0 used "U-" followed by eight digits, and allowed "U+" to be used
>  only with exactly four digits to
>  indicate a code unit, not a code
>  point.
> 
> 
>
It is just a convention to show that the value is Unicode. A bit like '0x' or 'h' for hex values (`0xB9` or `B9h`). Why `0xB9` and not `0hB9` (or `&hB9` or `$B9`)? Just because that's how the coin flipped :-)