What is the purpose of a cross-reference table?

Cross Reference Tables or can say XREF tables are used to tracking the linage of data. Data contains records so XREF tables include the start and end date values of that records and In this if the same column is given by multiple source systems,XREF tables store all the values from all source systems. Cross Reference table is a database table and with help of this rows are links in two or more than two tables.