Steckklemmen - What is the difference between a plug-in terminal and a screw terminal?

The difference lies in the way in which the conductor is fixed in the terminal. Once you have inserted the conductor into the opening, a plug-in terminal will clasp it tightly. If you want to free the conductor, you need to push the release at the front. With screw terminals you need to fix the conductor yourself by tightening the screw.