Bitcoin is often referred to as a currency. And the general name 'cryptocurrency' giving to all digital assets presents them as currencies although having a deeper meaning, hence
cryptic currenciesA currency is an object generally accepted in a certain region as a means of payment. Asides the Euro which is used by different countries, each state usually has its own accepted currencies.
Where do currencies get their value?
Currencies are legal tenders stipulated by governments of each nations. And there are financial institutions, usually banks which decides the value a currency has. This could be bank notes, coins, mobile money or codes on a debit card, these can all be classified as fiat money.
There is also
Commodity Money. This includes commodities like, gold, silver, diamonds, coal, salt or any commodity which has a value based in its qualities and applications.
Unlike fiat money, these has intrinsic value and are not supported or directly controlled by any financial institution which dictates it's price.
So, is bitcoin classified as fiat money or commodity money?
The above question is better asked as, is bitcoin a currency whose value is determined by what people take it to be or is it based on its intrinsic value and practical applications.
I would say it is a little of both.
Bitcoin is a decentralized protocol with no central control system or official institution which would regulate and determine it's price. Although the bitcoin core and miners pool have a certain level of influence and control on its value. But the community can equally and more effectively affect it's value through demand and supply.
Bitcoin is also a digital asset built on a technology (blockchain) it is borderless and transactions are cheap. And it's value which seems to be consolidating with time, makes it an investment option as well.
What are the limitations of bitcoin? Bitcoin as a payment option faces a huge problems in government restrictions, adoption limitations and scalability.
With its tps being in the range of 3.3 to 7 transactions per second it can hardly compete with government controlled forms of transactions like VISA with an average of 47,000 tps.
But bitcoin was not created to compete but rather serve as an alternative to fiat currencies (and maybe commodity money also) and give users total control over their assets. Though with such a growing community there has been lots of suggestions on how to tackle the scale limitations. And many propositions this far, such as hardforks and Segregated witness, popularly called segwit
https://en.bitcoinwiki.org/wiki/Amp/Segregated_WitnessBitcoin Cash which was launched last year increased a blocksize to 7MB. There is still yet to be a consensus to approve Segwit.