I don't know what a composition editor is. But an information manager is, generally, one of the wide range of applications that take unstructured, file-like dat

I don't know what a composition editor is. But an information manager is, generally, one of the wide range of applications that take unstructured, file-like data and provide an application interface to them. What that entails varies, but there's often indexing (and powerful search), tagging, and sometimes NLP–a snippets manager, or a PIM like Eaglefiler, Together, Yojimbo, DEVONthink and many many more. EDIT: You might mean, "what's a composition interface?" In which case it's a text-editor component, with some added UI sugar like current line highlighting, word count, splitting, typewriting scrolling, full-screen mode, et cetera. You know, an interface for composing text.