The Visual LISP Developer's Bible - 2003 Edition - Autodesk

Some common collections within AutoCAD are Documents, Layers, Dimension Styles, Linetypes, Blocks and so forth. Some common dictionaries within AutoCAD are PageSetups, Layouts (yes, they are also stored as a dictionary), and various components of Express Tools such as WipeOuts. Xrecord objects are stored within dictionaries as well. ................
................