Until you move your Bitcoin to a private wallet , you technically hold an from the exchange rather than the asset itself. If an exchange fails, your "money" may be lost as you are considered a creditor to that company.
Real blockchain fees only occur when you withdraw your Bitcoin to a private wallet. These small amounts of BTC (not your initial fiat deposit) go to miners who secure the network.
All Bitcoin originally enters the market through miners. When you buy "newly" minted Bitcoin, you are essentially paying a miner for the computational work they performed to create that block. Ownership Risk: "The IOU"
Your money goes directly to the individual seller's bank account or mobile wallet, often facilitated by an escrow system on the platform.
Your dollars are moved into the exchange's bank account and then credited to the internal account of the person selling the asset.
