What is the mean of "Hide on Profile" and "Show on Profile"on fluther?

My guess would be anything you had the option to hide would not show on the profile accessible to the public or other Flutheronians. That which you show would be viewable to anyine who clicked on your profile; that would be my guess if it were similar to other sites.

Clicking “Hide on Profile” means neither you nor anyone else (except for perhaps administrative people), will be able to see that question or answer on your profile Overview. However, you and only you (except as mentioned before), can still see them in your Questions and Responses tabs.

Clicking “Show on Profile” means any questions or answers that were hidden, are now publicly visible on your profile Overview and in the aforementioned tabs.