The Unicode character is used both for a typographic apostrophe and a single right quotation mark. This is due to the many fonts and character sets that unified the characters into a single code point, and the difficulty of software distinguishing which character is intended by a user's typing. There are arguments that the typographic apostrophe should be a different code point, U+02BC modifier letter apostrophe|.
The straight apostrophe is even more ambiguous, as it could also be an open quotation mark, or a prime symbol.