This adapter board takes a arduino nano running grbl and connects it to e.g. tb6600 stepper boards.
You can use either terminal blocks or the JST connectors.
Some stepper have common ground others common +5V. This is selectable via jumpers.
Also you can change the spindle enable from simple enable to pwm (you also must change grbl to support pwm).
Furthermore there is a schmitt trigger with a RC filter for Limit Switches.