Why would I think about retirement?
Yes, we know, when you are young it is hard to think about retirement. You have other problems on your mind. However, you have surely heard around (or at least from Social Media) about many elderly people who "do not make ends meet with the pension." That is why, besides investments, it is good to transfer part of the excess income directly towards your future.
You can be content with the pension provided by the state: you pay contributions now for the current pensioners, and others will pay for your pension when you retire. However, it might be safer not to rely on others and to pay for yourself even now.
You can do this through a private pension fund or a simple life insurance. Both work the same: those who manage your money invest it and try to multiply it. Most of these administrators commit to returning at least what you have accumulated through your contributions to them, all adjusted for the inflation rate.
So, start thinking now about how you want your retirement life to look like.