Understanding Web Communications

Web applications have two distinct components as follows:

1. Client 
1. It is front-end interface. It consists of user interface, acceptance of input from users, sending of data for server processing.
2. Generally, web browser represent the user interface to user.
2. Server: 
1. It is back-end interface. It responds to request made by clients after processing input data.
2. Response consists of HTML pages that indicates instruction for web browser regarding generation of user interface.

The client (Web Browser) and Server (Web Server) communicate by using Hypertext Transfer Protocol (HTTP). It is a text-based network protocol assigned to TCP port 80. If the additional security is needed then server can apply for certificate, which allow you to use HTTP Secure (HTTPS). This will authenticate the server and encrypt the communication between server and client. HTTPS is assigned to port 443.