what is port in app.run flask code example

Example 1: how to change port in flask app

from flask import Flask
app = Flask(__name__)

@app.route("/")
def hello():
    return "Hello World!"

if __name__ == '__main__':
    app.run(host="localhost", port=8000, debug=True)

Example 2: how to change port in flask app

flask run -h localhost -p 3000