JRE included with JDK vs. standalone JRE

The "standalone JRE" (sometimes also referred to as the "Public JRE") generally does not contain the server version of HotSpot. It also lacks the tools included with the JDK (JavaDB, javac, tools.jar, etc).

Otherwise, the runtimes are identical. Also, note that a JDK may install one (or more) JREs.

Finally, all of the above notes are in regards to Sun's Java installers for Windows. Other vendors and platforms may (and sometimes do) vary.