importance of virtual environment setup for django with python
While I can't directly describe the experience with Django and virtual environments, I suspect its pretty similar to how I have been using Flask and virtualenv.

Virtual environment does exactly what it says - where a environment is set up for you to develop your app (including your web app) that does not impact the libraries that you run on your machine. It creates a blank slate, so to speak, with just the core Python modules. You can use pip to install new modules and freeze it into a requirements.txt file so that any users (including yourself) can see which external libraries are needed.
It has a lot of importance because of the ability to track external libraries. For instance, I program between two machines and I have a virtual environment set up for either machine. The requirements.txt file allows me to install only the libraries I need with the exact versions of those libraries. This guarantees that when I am ready to deploy on a production machine, I know what libraries that I need. This prevents any modules that I have installed outside of a virtual environment from impacting the program that I run within a virtual environment.
Yes and no. I think it is good practice to use a virtual environment for those above reasons and keeps your projects clean. Not to mention, it is not difficult to set up a virtual environment and maintain it. If you're just running a small script to check on an algorithm or approach, you may not need a virtual environment. But I would still recommend doing so to keep your runtime environments clean and well managed.
I am very much new to the process of development of a web-application with django, and i came across this setting up and using virtual environment for python.
So i landed with some basic questions.

What does this virtual environment exactly mean.
Does that has any sort of importance in the development of web-application using django and python modules.
do i have to worry about setting up of virtual environment each time
in the development process.