Stablecoins aim to hold a steady value, usually by tracking a currency like the US dollar. They are widely used, which is exactly why regulators pay close attention to them.
The concern is that a stablecoin could lose its peg, or that its reserves may not be as solid or transparent as assumed. If large numbers of people use them for payments or savings, problems could spread. That is why rules around stablecoins are developing in the UK and elsewhere.
Learn the basics in what are stablecoins.
Crypto is high risk and largely unregulated in the UK. You could lose all the money you invest, and most crypto is not protected by the FSCS or the Financial Ombudsman Service. This is educational information only, not financial advice. Only invest what you can afford to lose.