UserDefined... tables belong to the UserDefinedTable module or its successor "form and List" in DNN 5. This module allow to create custom lists and stores a various lists created in only 3 tables: UserDefinedFields does contain the column definitions, UserDefinedRow holds the rowID and UserDefinedData is used to store the real data per cell, i.e. using a row for each combination of rowID and FieldID.

{databaseOwner} is a variable for the dababase owner, "dbo" by default. this is used by SQL Server to specify ownership and permissions. Hosters have the option to ensure, multiple sites can be safely hosted on the same server w/o security risks.

{objectQualifier} is a prefix used for all database objects of a DotNetNuke installation. it had been originally intended to allow multiple DNN installations to share a single database (deriving from times, when SQL server database hosting has been rather expensive). The use has been leverages since the ASP.Net membership provider was used - its tables do not use the prefix. It can now be used to share a database with a different application and clearly display, which tables belong to DNN. ObjectQualifier and DatabaseOwner need to be specified in web.config file or installation wizard BEFORE the database is created and cannot be changed afterwards.

UserDefinedRows is the name of the table.