These tokens don’t have an inherent use case but are issued by a company to raise funds. They don’t give access to a service, but allow users to participate in the growth of the value of the company through, for example, buybacks of the tokens by the issuing company. This is still a very grey area in terms of regulations, and there have been frantic discussions on what exactly differentiates security tokens from utility tokens.
On the flip side, if the world suffers a global financial meltdown on the scale of the Great Depression or something similar again, and fiat currencies start to crater, it very well may be such that governments are forced to resort to accepting bitcoin and other cryptocurrencies, if enough people simply flat out refuse to put their stock in fiat. This was exactly what the US government was forced to do just 13 years into their original experiment with Continental currency, when they agreed to promise to back all the currency they issued with hard gold and silver.

From there, you’re ready to buy and sell Bitcoin based on the current market value. Rather than paying for a set amount of Bitcoin, you will tell the exchange how much money you want to trade, and they’ll break down how much Bitcoin you can buy. Unless you’re investing thousands of dollars into the cryptocurrency, you’re likely to be buying a fraction of one Bitcoin.
Please note that virtual currency is a digital representation of value that functions as a medium of exchange, a unit of account, or a store of value, but it does not have legal tender status. Virtual currencies are sometimes exchanged for U.S. dollars or other currencies around the world, but they are not currently backed nor supported by any government or central bank. Their value is completely derived by market forces of supply and demand, and they are more volatile than traditional fiat currencies. Profits and losses related to this volatility are amplified in margined futures contracts.