The rounded square icons are for the keyboard, while the circles are for controller. The keyboard key for "Interact" is the Space Bar. The "A" button is for the controller. You can also go into the settings and remap the keys if you'd prefer to use something different.
We will be adding the following to the list of controls in future games. We're still thinking on the best way to clarify icons like the Space Bar in the space available, though leaning towards adding tool tips.
Thanks for taking the time to comment and ask!