This assumes some knowledge of trading terms.  New stuff is concept of borrowing on a decentralized exchange.

Why trade with leverage?  you can magnify gains and risk by 2x - so more dangerous but also pays better. Additionally, higher leverage helps keep trading and providing liquidity profitable on smaller % changes helping stability - e.g. forex is often 50-100x leverage.

The DEX is interesting because you can actually borrow and move coins you borrow off the exchange. I borrowed a bunch of bitUSD when I thought BTS bottomed out, bought BTC with it, and moved it off exchange. I'll settle the debt in future if BTS is higher (and if not the loss is fine).

Smart contract on BTS blockchain is what holds your BTS as collateral and creates new bitUSD coins - not sure that counts as bank since there's no expectation of returning what you borrow. You can always hit settle on it and destroy the coin to get $1 of BTS out of the contract. If you never return bitUSD, doesn't matter, and you helped reduce supply of BTS increasing its value.

You can borrow bitUSD, and return it later, which will make 0 net difference. Shorting is the act of selling what you borrowed and buying it back at another cost to return later keeping the difference.

shorting a coin can also be thought as margin longing the coin you buy with the borrowed money.

tbh I found it fascinating and people introduced me to concept of stacking these - although have to keep in mind higher leverage = higher losses too.