The linux kernel provides drivers that you can use in order to read/write/use various devices.
Unlike Windows that creates a drive for hard drivers/cdroms/flash drives etc, linux creates a file with a set of instructions that allow you to access that device. That file is located in /dev/ and the process by witch you access it is called mounting
So you plug in the camera, the system detects it and it creates that file in /dev/ that you need to mount in order to access. Ubuntu usually auto-mounts the devices for you, and that is probably what you are experiencing there. The usual mount point for devices is in /media/ or /mnt/ depending on the linux distribution (for ubuntu it's /media/).
You can manually mount and unmount devices using the terminal (ctrl+alt+t) and executing the mount and umount commands which you can use the --help attributes on, read their manual pages using man mount and man umount or google about them.
You should read a little about the linux file system in order to understand how it does all this and how handy it becomes when you need to expand a folder size or create logical volumes.