Transaction logging is a process used in databases to record all changes made to the data. This log keeps a detailed history of transactions, including inserts, updates, and deletes. By maintaining this record, databases can ensure data integrity and recover from failures by reverting to a previous state if necessary. When a transaction occurs, the details are written to a log file before the actual changes are applied to the database. This approach, often associated with systems like SQL Server or Oracle, helps prevent data loss and allows for efficient recovery in case of crashes or errors.