The control bar is a collection of controlling buttons. It will be removed if there's no mouse activity. On touch devices you can toggle it by tapping the main picture.
Show text on buttons
A short explaining text will be added to the button. A longer text pops up when you move over the mouse. (This is not an option on touch devices though.)
Hide the "Fit screen/1:1" button
If you don't want the visitors to toggle between the "1:1 mode" and "fit to screen mode" turn this option off.
Hide the "Start/Stop" button
If you don't want your visitor be able to play slideshow, turn this option off.