Destination of postgre logs

Destination of postgre logs

I tuned the server's variables almost like told here, but the
log_destination is 'csvlog'. After that in the data directory:
the *.log file is empty.
the file with same name but with .csv extension holds the logs from the
server.
Explain me please -- this is correct behaviour?
If log_destination is 'csvlog' -- the output file will have the *.csv
extension, rather than .log?
What log_destination should be, to write logs in to the *.log file?
Thanks!