The different IDEs look similar, and have the same screen structure more or less. In the following screenshot, you can see an IntelliJ IDE:

On the left side, you can see the file structure of a Java project. A Java project typically contains many files in different directories which we will discuss in the next chapter. The simple HelloWorld application contains a pom.xml project description file. This file is needed for the Maven build tool, which is also a topic for the next chapter. For now, you should only know that it is a file that describes the project structure for maven. The IDE also keeps track of some administrative data for itself. It is stored in HelloWorld.iml. The main program file is stored in the src/main/java directory and named HelloWorld.java.

On the right side, you can see the files. In the screenshot, we have only one file opened. In case there is more than one file opened, then there are tabs-one for each file. Now, the active file is HelloWorld.java that can be edited in the source code editor.