Update README.md

README.md

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 webwork-open-problem-library
 =============================
 
-This is the WeBWorK Open Problem Library (OPL for short).  Here you
+This is the WeBWorK Open Problem Library.  Here you
 will find all WeBWorK problems contributed by the OpenWeBWorK
 community.
 
+This repository has three parts:
+  1. Contrib
+  2. Pending
+  3. OpenProblemLibrary
+
+The contents of OpenProblemLibrary are the problems one can browse via the Library Browser in webwork using hierarchical menus (Subject, Chapter, and Section).  While this whole repository is named webwork-open-problem-library, we will use OPL to refer to just this part.
+
+New contributions should go into Contrib.  The original contributors retain control of these files, both in style and content.  Problems are automatically considered for being added to the OPL unless the contributor specifically asks that they not be.  So, this can be an avenue for sharing webwork problems with the world exactly as the author has created them.  End users can browse and use problems directly from Contrib by making symbolic links from the templates directories of their courses.
+
+When problems from Contrib are being reviewed by the OPL Editorial Board for inclusion in the OPL, they are copied temporarily into Pending.  General users should ignore the contents of Pending since files will come and go.
+
 
 Notes
 -----