This isn’t an ESP8266 shield, either: you can write code for the ESP module, connect the serial pins, and hit the program button. The basic functions of the Arduino IDE – pinMode, digitalRead ...

Arduino microcontrollers have added Python to the range of compatible programming languages. Others can be used, and not just Arduino's own IDE app.

M4N asks:. Is there a reason why functions in most(?) programming languages are designed to support any number of input parameters but only one return value?

The Java program can also read an Arduino program file and convert all the print calls in it to use the library, if you like. As you might expect, this requires some cooperation from your program.

Arduino libraries, like libraries for other programming languages, help easily extend the range of functions available to users in the standard integrated development environment (IDE).