1. The coins are created by users who "mine" them by lending computing power to verify other users transactions which use blockchain technology.They receive Bitcoins in exchange.
Bitcoin is not created by miners but is mined by miners, the same thing as gold, which is not created by gold miners, but the gold already exists. So to process Bitcoin transactions, validation is needed from a device, Bitcoin miners are tasked with processing these transactions and for every successful transaction the miner gets Bitcoin, so they never create Bitcoin.
2.The coins also can be bought and sold on exchanges with US dollars and other fiat currencies(the physical money we use every day in our bank accounts).
That's right, almost 99% of fiat currencies around the world have BTC pairs
(poor countries, developing countries or developed countries), Bitcoin has become part of the world economy now so everyone around the world is free to transact with Bitcoin using the pair their own country's fiat currency.
3. Bitcoins have to be stored in a digital wallet, either online through an exchange like Coinbase, or offline on a hard drive using specialised software.
Yes, this is basic knowledge about how to store Bitcoin safely and to avoid hacking, so far there are various kinds of Bitcoin wallets available, such as Bluewallet, Electrum, and so on, just adjust it to your needs, many also recommend holding large amounts in the long term, using a paper wallet is a wise choice.