Here's the exam objective that you referred:
7.1 Describe at a high level the basic characteristics, benefits and drawbacks of creating thin-clients using HTML and JavaScript and the related deployment issues and solutions.
First of all, note that a thin-client is a program on a system, that utilizes the power/ resources of a server and displays the result to a user on the client. Thin-clients have limited processing power and capabilities.
Web pages designed using HTML and JavaScript are referred to as thin clients because they connect to a server to process data collected from a user, and display the output back in the browser. Web pages have limited processing power and capabilities. Compare it with fat-client, for example, a gaming application created using Swing. This game will process players next move, other data on the client itself.
For this SCJA exam objective, understand what is HTML and Javascript, their capabilities and limitations, challenges involved in using these technologies and how you can resolve them.
You can easily get info on HTML and JavaScript using any search engine.
cheers
Mala