What Turns Your Text Into Something That Runs

Four things this topic established, and where each one was.

What the topic established, and which card it was on
The thing	Where
Java translates twice: text to bytecode, then bytecode to processor instructions	Why Your .java File Is Not a Program Yet
`javac` writes a `.class` file; `java` takes a class name and runs it	One Command Writes a File, the Other Reads It
The bytecode is identical everywhere; the JVM is what is built per machine	The Same Build Artefact on a Laptop and on a Linux Server
The JDK contains the JRE, which contains the JVM — install the JDK to compile	JDK, JRE and JVM: Which One You Actually Install
The JVM looks for one exact `main` signature and reports nothing until you run it	It Compiled, and Then Said No Main Method Found

A failure's timing tells you which translation caught it. Compile-time means the text was not valid Java. Runtime means it was, and something about the world was not what the code assumed.