The single-channel relay module is much more than just a plain relay, it comprises of components that make switching and connection easier and act as indicators to show if the module is powered and if the relay is active or not.
It can be used as a single chip module for appliance control and work with both DC or AC signals where you can control the 220V AC load.
High-level trigger refers to the signal voltage between input and trigger, can be understood as a signal input with VCC cathode short-circuit triggered a way;
Low-level trigger refers to the signal voltage between the input terminal and Earth OV trigger, can be understood as a signal input terminal and the GND negative electrode short circuit triggered is a way 1-channel relay module connection.
