I think they have said it all or almost said it all but I want to add this to it, just like they said Fiat is our local money we use every day to buy something and sometimes even give people to send us crypto that is exchange and so Fiat doesn't change value, it is more like a fixed something, Naija 50 naira remains 50 naira forever though others countries currency do vary in the crypto world while Bitcoin is an asset that can be invest on because of it volatility meaning that the value of Bitcoin is not fixed like Fiat, Bitcoin value changes at any point in time.
Fiats is just another name for the currency of different countries and nothing more because if you dey use all those explanations, don't forget that you can buy dollars today to make a fortune tomorrow when the value of Naira drops and you sell your dollars back to Naira to have more money so fiats can still be invested in when you exchange them. Currency (Forex) trading is a thing and one of he best ways of making money. Fiats are also volatile but not as much as Bitcoin abi una no dey see the way Naira dey fall and rise, what do you think that is if not volatility. Fiats na just money, na just say na the way, wey oyinbo dey call am. Fiats no bad to hold too because if you no get cash, na your Bitcoin you go dey sell to take chop so while you invest in Bitcoin, have some cash around.