GraalVM is a project based in Oracle Labs developing a new JIT Compiler and Polyglot Runtime for the JVM. Further details can be found on the OTN site.
Graal SDK contains long term supported APIs of GraalVM.
Graal is a dynamic compiler written in Java that integrates with the HotSpot JVM.
Truffle is a framework for implementing languages and instruments that use Graal as a dynamic compiler.
Tools contains a set of tools for Truffle guest languages implemented using the instrumentation framework.
Substrate VM is a framework that allows ahead-of-time (AOT) compilation of Java applications under closed-world assumption into executable images or shared objects.