what is use of python flask code example

Example 1: python flask

from flask import Flask

app = Flask(__name__)

@app.route('/')
def index():
  return "Hello world!" #if you want to render a .html file, 
                        # import render_template from flask and use 
                        #render_template("index.html") here.

if __name__ == '__main__':
    app.debug = True
    app.run() #go to http://localhost:5000/ to view the page.

Example 2: what is flask

Flask is a web framework written in Python. 
This means flask provides you with tools, libraries and technologies that allow you to build a web application.

Here a a few resources for learning Flask (I have not personally used them before):
	https://youtube.com/playlist?list=PLzMcBGfZo4-n4vJJybUVV3Un_NFS5EOgX
    https://realpython.com/tutorials/flask/
    https://opensource.com/article/18/4/flask