In SharePoint Server terminology, web applications are the constructs that are used to provide the configuration and hosting infrastructure for SharePoint site collections. Each web application starts with an Internet Information Services (IIS) website. Each individual web application is connected to its own IIS website (using either a unique or a shared application pool). Frequently, each IIS site is configured with a unique domain namespace, which can be used for both application structuring and topology, as well as a security measure to mitigate cross-site scripting attacks.
Each web application has at least one content database associated with it. SharePoint Server 2016 and SharePoint Server 2019 both support up to 20 web applications per farm. Since each web application has an IIS site associated with it, you can only have one (by default) that answers on port 80 or 443. In previous versions of SharePoint Server, you could accomplish...