Your confusion dey very valid because I have been there before, though I didn't make a post about it but in my early days in the forum I have asked myself similar question about the meaning of fiat and I no go lie I got to know about the meaning few months ago because I've seen many users use it in their comments and I got to figure it out by myself because I felt embarrassed to ask about something so small. Just like other forum users have said, fiat simply means the cash or money you have at hand or in your bank account.