Spread betting is a clever way to get around paying tax on gains when playing the stock market. Rather than buying the underlying asset and having to pay stamp duty, you pay more on the spread but no tax.
Disclaimer, this site is hyperbole. Do not bet anything you cannot afford to lose.
Take professional advice before making financial decisions. The degenerates on Wall Street Bets are betting. This bull market is unprecendented and will it will be ugly if the market turns bearish.