This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
A client-server application could perform some processing on the client. For example, an applet that communicates with a server can be a client-server app. A web based client-server app is also known as a thin client.
A web portal is a web site that offers many services (e-mail, search engine, news, ...)
As far as I know a web application and a web enabled application refer to the same thing. (thin client app)