As you've probably guessed by now, deploying a web application is just the process of copying your web application files to a web server. By taking this step, you accomplish three things:
You ensure your web applications are available even when Visual Studio isn't running.
You allow users on other computers to run your web applications. (The Visual Studio web server handles only local requests.)
Your web application URLs will no longer need a port number.
Depending on your organization, you may be in charge of deploying web applications, or a dedicated web administrator may handle the process. Either way, it's worth learning the deployment process, which is quite straightforward.