What does the servlet value signify

I am getting a bit confused here. In our application we are having a few servlets defined. Here is the excerpt from the web.xml for one of the servlets:

<servlet>
    <servlet-name>AxisServlet</servlet-name>
    <display-name>Apache-Axis Servlet</display-name>
    <servlet-class>com.foo.framework.axis2.http.FrameworkServlet</servlet-class>
    <load-on-startup>0</load-on-startup>
</servlet> 

As per my understanding the value for the <load-on-startup> has to be a positive integer in order for it to get loaded automatically. I looked up on google but the responses I came across only added to my confusion.