A pension plan is an account where you put money now and take it out when you retire. It's forced saving, which is actually good.
Why it exists
Governments know people don't save. So they created pension plans with tax advantages to force you to save for retirement.
The tax advantage
If you put 1500 euros in a pension plan, you reduce your tax base by 1500 euros. That means you pay less taxes. It's money the government lets you save.
How it works
You save money monthly in the plan. That money gets invested in funds (stocks, bonds, whatever). It grows over 30-40 years. When you retire, you take it out.
It's not money for today
Here's the trick: you can't take this money out until you retire (with a few exceptions). It's forced saving on yourself.
Fees eat money
Some plans have crazy high fees (1-2% annually). Others are cheaper (0.3-0.5%). Pick plans with low fees.
Combined with compound interest
You save 100 euros monthly for 40 years. It grows with compound interest. When you retire, you have 150,000+ euros. Without doing anything special.
It's not perfect
Public pensions will probably drop in the future. Pension plans are a complement, not the complete solution. But something is better than nothing.
Start early
The earlier you start, the more time your money has to grow. At 25 vs 45, the difference after retirement age is brutal.