Transaction Tables

The section on undo tablespaces includes, “When the first DML operation is run within a transaction, the transaction is bound (assigned) to an undo segment (and therefore to a transaction table) in the current undo tablespace.”

What’s a transaction table? I don’t recall them being mentioned before this point, and there’s no forward link from here either. It’s not in the glossary, and the index only points to a description of how they are recovered, not what they are.