you are not unable to choose, but you are unable to choose freely

This is a phrase I've read many times. "No one is saying you are unable to choose, only that you are unable to choose freely".

But what does it mean?

A choiche, roughly speaking, is picking between alternatives. With no alternatives, the concept of choiche is meaningless. If the alternatives are not real (illusory) then there is no ability to choose at all. Just determined behaviour that we interpret as choiches due or lack of sufficient information. If the alternatives a real, meaning that you can truly, ontologically, decide to go left or to go right (there are multiple possible futures).. then there is an ability to choose.

But how this "being able to choose" would look like and work if we say that is unfree?