Spring : Need for the contextConfigLocation?

In web.xml we have context parameter set named contextConfigLocation and defined as shown in the below code:

<context-param>
    <param-name>contextConfigLocation</param-name>
    <param-value>/WEB-INF/root-context.xml</param-value>
</context-param>

Also the same parameter is set in the Dispatch Servlet as shown below

<servlet>
    <servlet-name>spring</servlet-name>
    <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
    <init-param>
       <param-name>contextConfigLocation</param-name>
       <param-value>/WEB-INF/servlet-context.xml</param-value>
    </init-param>
    <load-on-startup>1</load-on-startup>
</servlet>

What is the difference between these two contextConfigLocations ?