Что такое дескриптор развертывания

<?xml version="1.0" encoding="UTF-8" ?>
<web-app xmlns="http://java.sun.com/xml/ns/j2ee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd"
    version="2.4">

    <display-name>Display name.</display-name>
    <description>Description text.</description>

    <servlet>
        <servlet-name>ExampleServlet</servlet-name>
        <servlet-class>xyz.company.ExampleServlet</servlet-class>
        <load-on-startup>1</load-on-startup>
        <init-param>
            <param-name>configuration</param-name>
            <param-value>default</param-value>
        </init-param>
    </servlet>

    <servlet-mapping>
        <servlet-name>ExampleServlet</servlet-name>
        <url-pattern>/example</url-pattern>
    </servlet-mapping>

    <context-param>
        <param-name>myParam</param-name>
        <param-value>the value</param-value>
    </context-param>
</web-app>