Then what does 'physical structure' mean according to Ref link where Architectures are described only?
The SQL Server transaction log operates logically as if the transaction log is a string of log records.
Conceptually, the log file is a string of log records. Physically, the sequence of log records is stored efficiently in the set of physical files that implement the transaction log.
The SQL Server Database Engine divides each physical log file internally into a number of virtual log files (VLFs).