Webserver APIs (from both Netscape and M

My technology literacy is not very high – therefore, my question – Currently a component of aa architectual system is implemented using Webserver APIs from both Microsoft and Netscape (ISAPI and NSAPI) and they are migrating to J2EE. Could you please explain the differences, including the benefits and disadvantages of migration to J2EE. Also how long cumbersome is this process? Finally, what do you need to do in order to roll-out the new architecture to your existing client base? How difficult is this? Finally, in layman terms is it possible to explain what J2EE does?