Q. What are we doing here?

A. Writing computer programs in the language called Java.

computer program A sequence of instructions suitable for processing by a computer.

In Java you can have many kinds of programs including:

applet (Java) A program that runs in the context of a browser
application (Java) A program that runs when translated by a Java compiler

We write our programs in an IDE such as Ready to Program. Our programs must use correct syntax and semantics so that they can be translated into binary by the compiler.

IDE (integrated development environment) A programming tool that gives programmers a single environment (that is, the hardware and software environment in which the program runs) for building programs rather than using individual editors and debuggers.

compiler A program that translates a source program into machine code that can be converted into an executable program (an object program)

syntax The rules that govern the structure of language statements; in particular, the rules for forming statements in a source language correctly.

semantics The relationships of characters or groups of characters to their meanings, independent of the manner of their interpretation and use.
debugging tool A program used to detect, trace and eliminate errors in computer programs or other software.