You fund a bit to the state pension and a bit to a private pension. Based on a previous comment Estonia allowed you to cash out the private pension. I assume. Romania has something similar where you pay for your state pension, mandatory level 1 private pension, and optionally a level 2/3 private pension. State + level 1 private pensions work as you'd expect, whereas level2/3 generally have cash-out terms. It's not either/or, if you want a level 3 private pension you need to contribute to both level 1&2.

edit: replace level with pillar, as I couldn't think of the word and saw it used by sibling comment after posting.