Q.1. Why we need node js to start appium server?

Ans:

If Appium tools are written in Node then you Need node to run it.

If they were written in Python then you would need Python.

If they were written in Java then you would need Java.

You need a correct runtime to run every software unless it is compiled into machine code

and saved as a native binary for the given architecture, which is not the case with JavaScript/Node

(or Python, Java, Perl, Ruby, etc.).

When you go to the Appium's source code,

you will see that it needs Node and which version it needs, in the package.json file:

  "engines": {
    "node": ">=4",
    "npm": ">=3"
  },

Answer taken from: 
https://stackoverflow.com/questions/43048995/why-do-we-need-node-js-to-be-installed-on-system-before-running-mobile-automatio