A SharePoint 2013 web application is composed of an Internet Information Services (IIS) web site that acts as a logical unit for the site collections that you create. Before you can create a site collection, we must first create a Web application. Each web application is represented by a different IIS web site with a unique or shared application pool. we can assign each web application a unique domain name.
When you create a new web application, you also create a new content database and define the authentication method used to connect to the database. In addition, you define an authentication method to be used by the IIS Web site in SharePoint 2013.
Let’s start by navigation to the SharePoint Central Administration.here we will find under Application Management, Click on Mange web application link Button
This page you can see which are already running web applications,now we have to create new web application then Click on New Button.
After Click ok Button It will take few Seconds to create web application
Once the web application is created, the following pop-up will come and here will be provide to create a site Collection