How to use dd command in linux

wiz@deb-DOC:~$ sudo dd if=/home/wiz/crunchbang-11-20130506-amd64.iso of=/dev/sdb bs=4M; sync
[sudo] password for wiz:
184+1 records in
184+1 records out
774897664 bytes (775 MB) copied, 0.867016 s, 894 MB/s