What is the role of java in web designing​?

Question

what is JavaScript?

Answer 1

Firstly, Java and JavaScript are different languages and just happen to have the same name.
JavaScript is used to make your website come alive and more interesting.
Java is a programming language, not a web coding language.

Answer 2

There are two ways how to use Java for web creating.
The first, as a Java applet, included into HTML page (although in is an older methodology, not used so much now).
And the second, as the web backend - in the server (simillary like PHP),
But in all these cases, Java is not the main source for web (graphics) design, but more for dynamic web programming (computing, or transfer data between web page and databases, and so on)