As Jeanne wrote, Task Manager (and any other operating system-based tool that reports process memory usage) reports the memory used by the
java process. This includes the amount of heap allocated, the code for the JVM, the data structures used by the JVM, and so on.
Java-based tools, such as JConsole, VisualVM, and JProfiler, report on heap usage. This is always a subset of the full memory used by the java process.