diff --git a/GB_set_user_data and GB_get_user_data.md b/GB_set_user_data and GB_get_user_data.md
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--- a/GB_set_user_data and GB_get_user_data.md	
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-## Definition
-
-<tt>void GB_set_user_data([[GB_gameboy_t]] *gb, void *data);</tt>
-
-<tt>void *GB_get_user_data([[GB_gameboy_t]] *gb);</tt>
-
-In `gb.h`
-
-## Description
-
-TBD
-
-## Thread Safety
-
-`GB_set_user_data` and `GB_get_user_data`  thread-safe and can be called from any thread and context.
diff --git a/GB_set_user_data-and-GB_get_user_data.md b/GB_set_user_data-and-GB_get_user_data.md
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+## Definition
+
+<tt>void GB_set_user_data([[GB_gameboy_t]] *gb, void *data);</tt>
+
+<tt>void *GB_get_user_data([[GB_gameboy_t]] *gb);</tt>
+
+In `gb.h`
+
+## Description
+
+`GB_set_user_data` can associate an arbitrary pointer with an emulator instance, and `GB_get_user_data` can read the associated pointer back. They can be used by a frontend that can handle multiple emulator instances to associate an emulator instance with its frontend data (For example, a window object that displays the screen of the instance) and read it back when getting callbacks.
+
+## Thread Safety
+
+`GB_set_user_data` and `GB_get_user_data` thread-safe and can be called from any thread and context.