Who or what entity controls the supply of bit coin? Who controls their “manufacture”.
When you "invest" in a fiat currency, willingly or unwillingly, you're holding money with serial numbers. The money printers promise you that they're difficult to counterfeit so you don't have to worry about duplicate serial numbers. (Yet they're counterfeited all the time, mostly by hostile nations but also by the issuing nation when sending billions to foreign terrorists such as Iran).
The money printers do NOT ensure they won't print more money with new serial numbers that devalues your fiat money. In fact, they're printing more all the time. The value of your fiat money is what the printers say it is by adding or removing some from circulation.
Cryptocurrencies on the other hand promise you a distinct serial number that's difficult to counterfeit since each transaction tracks the serial number (unlike transactions with bills). Cryptocurrencies offer a fixed number of digital "coins" or at least a schedule of how long it takes to "mine" new ones and how many might be added. The market then determines the value of each "coin".
There is no central authority for Bitcoin. There is no “President” of Bitcoin. You are able to hook a “mining rig” up to the internet and compete for new “coins” against the rest of the world.
Bitcoin mining is based on a reward system for computing/puzzle solving algorithmic ledger information block-chains based on computer processing power. (I’m oversimplifying this down a lot)
Basically at this point it takes a long time for a single computer or multiple ones to generate a single Bitcoin that is encrypted because the rewards are becoming scarce now.
That’s sort of why its said to be digital gold because it is impossible to flood the market with new bit coins. There is also a finite amount of Bitcoins that can be rewarded. After they are all mined out the entire market wont have anymore room without some new kind of computer I think.