Compound growth is the process by which an investment generates earnings, and those earnings then generate their own earnings, and so on — growth building on growth. It's the engine behind long-term saving and investing, and the reason starting early matters so much.
Imagine £1,000 growing at 7% a year. After year one it's £1,070. In year two, you earn 7% not just on the original £1,000 but on the £1,070 — so you earn slightly more. Each year the base grows, so each year's growth is larger than the last. Over short periods the effect is modest; over decades it becomes dramatic, as the later years' growth dwarfs the early contributions.
Because compounding rewards time so heavily, money invested in your 20s can outgrow much larger sums invested in your 40s. Someone who invests modestly but early often ends up with more than someone who starts later with bigger contributions — the early money simply has more years to compound. This is why the most valuable thing a young saver has isn't a high income; it's time.
Start as early as you can, even with small amounts, and let time do the heavy lifting. The same principle works in reverse with debt — which is why high-interest debt is so costly. This is general information, not financial advice.