/cdrom /media /mnt

/media : Mount point for
removeable media

Purpose

This directory contains subdirectories which are used as mount points for
removeable media such as floppy disks, cdroms and zip disks.

Rationale

Historically there have been a number of other different places used to mount removeable media such as /cdrom, /mnt or /mnt/cdrom. Placing the mount points for all removeable media directly in the root directory would potentially result in a large number of extra directories in /. Although the use of subdirectories in /mnt as a mount point has recently been common, it conflicts with a much older tradition of using /mnt directly as a temporary mount point.

Specific
Options

The following directories, or symbolic links to directories, must be
in /media, if the corresponding subsystem is
installed:

On systems where more than one device exists for mounting a certain type of
media, mount directories can be created by appending a digit to the name of
those available above starting with ‘0‘, but the unqualified name must also
exist. [16]

/mnt : Mount
point for a temporarily mounted filesystem

Purpose

This directory is provided so that the system administrator may temporarily
mount a filesystem as needed. The content of this directory is a local issue and
should not affect the manner in which any program is run.

This directory must not be used by installation programs: a suitable
temporary directory not in use by the system must be used instead.