New to axis2. Question on transport classes

[Jim Akmer]

Hi,

Could someone please explain what is the use of a TransportReceiver/TransportSender e.g. CommonsHTTPTransportSender in axis2?
Isn't the HTTP part being handled by the container e.g Tomcat?
What is the functionality of these transport classes then?
E.g. when in services.xml there is the following:

<transports>
         <transport>https</transport>
</transports> 

whys is it needed?

Could someone please help me on this?

Thanks!