Each time we visit a URL in a browser, it makes a request to the web server, which processes the request and returns a response back to the browser. In our Flask app, we can create endpoints to handle the various requests. Requests from different URLs can be directed to different endpoints in a process called routing.

To build a route, we need to first define a function, known as a view function, that contains the code for processing the request and generating a response. The response could be something as simple as a string of text. Then, we can use the route() decorator to bind a URL to the view function such that the function will be triggered when the URL is visited:

@app.route('/')
def home():
    return 'Hello, World!'

The route() decorator takes the URL path as parameter, or the part of the URL that follows the domain name. All URL paths must start with a leading slash. In the above example, if we visit http://localhost:5000/ in the browser, Hello, World! will be displayed on the webpage.

Multiple URLs can also be bound to the same view function:

@app.route('/')
@app.route('/home')
def home():
    return 'Hello, World!'

Now, both http://localhost:5000/ and http://localhost:5000/home will display Hello, World!.