This option allows you to refine the component with all of the required properties as defined in DxDataBook, it is part of the verification process. If you load a component to DxDataBook it will search the library (tables) and show the matching components based on the properties currently on the symbol. Say for example you have a resistor with a Value of 2.2k but no other properties, when you load this into DxDataBook it will list all resistors with a matching value of 2.2k. You can then select the precise component you require based on other properties such as Cell name (AKA footprint/decal) or tolerance etc. Then have DxDataBook annotate these properties back to the schematic.
It does not allow you to add a new component to the DxDataBook tables from the schematic, you can only do this from the Central Library or DxDataBook itself (or your data source).
This is a great answer. Much better than what is in the manuals and help files. Mentor needs to add this to the help file.