Inflation is when everything gets more expensive. Your money buys less. That's it.
10 years ago vs now
A coffee cost 1 euro. Now it costs 2. Gas was 1.20 per liter. Now it's 1.50. Everything goes up. Your money is worth less.
Why does it happen
Governments print money, there's more money in circulation, prices go up. It's like everyone suddenly earned double but everything costs double. Prices rise, period.
How it affects your wallet
If you have 1000 euros under your mattress and do nothing for 10 years, that money now buys what 700 euros used to buy. You lost 300 euros doing absolutely nothing.
The easy solution
Invest your money in things that rise faster than inflation. Stocks, houses, bonds. That way your money doesn't lose value. Rich people know this, that's why they invest.
When it's a real problem
When inflation hits 10% annually or more, everything gets expensive fast. When salaries don't rise but prices do. That hurts.
The good news
Normal inflation (2-3% annually) is actually good for the economy. The problem is when it gets out of control.