What is ' and why does Google search replace it with apostrophe?

In what language does and - hash - three - nine - semicolon (') represent the apostrophe? I had some website data extracted in JSON format where some of the user comments had apostrophe which were replaced by '.

So, what representation it is? I can not even google it as Google searches for apostrophe and not for and - hash - three - nine - semicolon.

It's HTML character references for encoding a character by its decimal code point

Look at the ASCII table here and you'll see that 39 (hex 0x27, octal 47) is the code for apostrophe