TCP/IP is a lower-level protocol whose job is to get data reliably from one computer to another. HTTP is a higher-level protocol, which is used to move requests from a client to a Web Server and responses from a Web Server to a client.
A2:
It stands for the Model-View-Controller architecture.
A3:
An MVC design subdivides the task of creating an interactive system into logical subsystems. By grouping these functions logically, you get an easier design to understand and modify.
A4:
Session Beans can be used for the Controller layer, and Entity Beans can be used for the Model.