What is there inside the WebRowSet xml file ?

RowSet objects are not same as ResultSet object which contain only data. They also have properties and metadata about their columns.
XML document representing a WebRowSet object includes these following:

1-Properties: These properties describe standard synchronization provider properties including general RowSet properties.
2-MetaData: This describe the metadata associated with the tabular structure used by a WebRowSet object. This is mostly same as ResultSet.
3-It describes the original data.