Creating mounting point

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http://unix.stackexchange.com – I am mounting an image, and just realized that I have to create the directory for mounting point first. The command mount won't mount to a non-existing directory. But I seem to remember in some cases, when I insert some external device, such as external HDD and CD, I don't have to create mounting point myself. So I wonder when mounting points are required to be created by myself and when not? Is it correct that mounting point directories can be created anywhere? Then what is the purposes of the directories /mnt and /media? Aren't they for hosting mounting points of devices? PS: I am unde (HowTos)