When Eclipse deploy web application in the existing Tomcat server, it will create Context element in server.xml.
The details of Context element in Tomcat is
The Context element represents a web application, which is run within a particular virtual host. Each web application is based on a Web Application Archive (WAR) file, or a corresponding directory containing the corresponding unpacked contents, as described in the Servlet Specification (version 2.2 or later). For more information about web application archives, you can download the Servlet Specification, and review the Tomcat Application Developer’s Guide.
You can find more details from the following URL.