" (disambiguation) explained

is a punctuation mark used in pairs in various writing systems to set off direct speech, a quotation, or a phrase.

also resembles other characters, and is sometimes substituted for them:

• Double prime, used for:
  • Inch, a unit of length in the United States customary and the obsolete (British) Imperial systems of measurement
  • Arcsecond, a fraction of an arcminute
• Ditto mark, a typographic symbol indicating that the word(s) or figure(s) above it are to be repeated
• Gershayim, a typographical mark in the Hebrew language
• Modifier letter double apostrophe, a modifier letter used in the Tundra Nenets and Dan languages