Right now, your money is sitting somewhere. Probably a current account. And every day it sits there, it is losing value.
The reason is inflation. Prices rise every year. If your money earns less than the rate of inflation, it can buy less next year than it can today.
In 2000, £100 bought roughly what £175 buys today. Money that sat in a jar under the bed has quietly become less valuable — not because anyone took it, but because everything else got more expensive.
Investing is how you try to make your money grow faster than inflation. Instead of sitting still, it works for you.
Islam encourages productive use of wealth. Hoarding money while it loses value benefits nobody. Trade, investment, and enterprise are all encouraged in Islamic teaching. What is prohibited is riba — earning from lending money at a fixed, guaranteed rate regardless of real outcomes.