It doesn't matter where you mount the partition - for all you care you could be mounting it in /usr/bin, and it would still be accessible. But, it's advisable to mount it to /mnt because then you can have all mounted partitions in the same directory (and /mnt is the default on most systems). Wherever you mount it, you information will still be written to the partition/drive, and you'll have no problems if you 'umount' them before unplugging them (although on most current systems the information will be transferred automatically, without waiting for the unmounting process to write the files over).
The point of linking to /mnt from /home is that when you open your home folder all you've gotta do is click on the link to /mnt to take you there - instead of having to type it into the address bar each time.
A 'folder' is a 'directory' in UNIX. I hope it's clearer now.
Ps. You might want to read up on a few of the links here
to help you - especially the "Linux File Systems - Explained" one.