Question: Can someone explain the differences between GraalVM and Jvm-Hotspot, and how GraalVM is related to OpenJDK's HotSpot.

Answer: 
In that context you could think of GraalVM as a modified/improved HotSpot JVM [very loosely: OpenJDK's HotSpot + the Graal JIT Compiler (replacing the one from HotSpot) + the ability to run other languages (JS, Ruby, R, Python, etc.) + ability to AOT compile Java 
 + additional bundled tools, etc.]
Detailed information about how Graalvm performs better than standard Hotspot and how to use it: <https://www.baeldung.com/graal-java-jit-compiler>