When you specify the [Object] data type, you enable the display of the Object type, Object stereotype, and Inverse collection name fields.
The Object type field specifies the kind of object you want to link to, and the stereotype field allows you to filter the objects that are available for selection.
For example, under the Table metaclass, I create an extended attribute called Owner, select [Object] in the Data type field, and User in the Object type field. I name the inverse collection "Tables owned". I can set the Owner attribute in the property sheet of a table, and the table will be listed on the Dependencies tab of the user property sheet, under the name of "Tables owned".