Right now, this class abstracts the following execution scopes: Method, Closure, Module, Class, MetaClass Top-level Script, and Eval Script In the compiler-land, IR versions of these scopes encapsulate only as much information as is required to convert Ruby code into equivalent Java code. But, in the non-compiler land, there will be a corresponding java object for some of these scopes which encapsulates the runtime semantics and data needed for implementing them. In the case of Module, Class, MetaClass, and Method, they also happen to be instances of the corresponding Ruby classes -- so, in addition to providing code that help with this specific ruby implementation, they also have code that let them behave as ruby instances of their corresponding classes. Examples: - the runtime class object might have refs. to the runtime method objects. - the runtime method object might have a slot for a heap frame (for when it has closures that need access to the method's local variables), it might have version information, it might have references to other methods that were optimized with the current version number, etc. - the runtime closure object will have a slot for a heap frame (for when it has closures within) and might get reified as a method in the java land (but inaccessible in ruby land). So, passing closures in Java land might be equivalent to passing around the method handles. and so on ...