Relationship between HotSpot and JVM, JDK / OpenJDK?

It is one of the JVM implementations, among the many existing . It is not the original implementation of the JVM, but soon became the official one. Created by Sun today owned by Oracle, but based on something already in place for another language in another company purchased by Sun. The great innovation of it was the inclusion of a JITter adaptive looking for the best native code according to the need of the code that is running. This is one of the strengths of Java allowing performance to often compensate for some weaknesses in the infrastructure that gives the default flexibility and security of the virtual machine.