What is the keyboard shortcut in the VBE of Excel VBA?

I want to use some keyboard shortcuts when I am developing in VBA. The specific operation is to switch between different modules. I believe there exists a shortcut very similar to the global shortcut for switching between two or more Windows windows, ie, Alt-Tab. But the two modules does not lay in two standard windows. They lay in two embedded small windows inside the VB Editor. And I am not sure what the name of the small window is. I believe they do have a formal name, which is called XXX window, where XXX is an abbreviation of 3 words. Does anybody still remember the terminology and the keyboard shortcut?