digitalWrite() and digitalRead()
Switch outputs and read inputs as HIGH or LOW.
Example
digitalWrite(pin, HIGH); // or LOW int v = digitalRead(pin); // HIGH (1) or LOW (0)
An input reads HIGH above roughly 60 % of the supply voltage (3 V on the Uno, about 2.5 V on the ESP32) and LOW below about 30 %. In between the result is undefined — another reason to avoid floating inputs.