Don't know about the structure in France.
But, usually in Europe, a portion of your taxes, as long as you're working, despite your age, goes into your retirement fund .
Then that money is being used to buy Tbills & to get long into various investments, and from the returns you're being paid that pension.
You can save for the retirement, on top of that freely through various products.
Well not everywhere - some countries have Pay-As-You-Go system, where current payments of the working population fund directly the pensions of the current retirees.
This is Pillar I. Pillar II are various employment contributions, where not every company unfortunately contributes and Pillar III is what you save on your own.
