can any let me know what is mounting and mount point
Mounting is the act of mounting or attaching some form of media; hard drive, CDROM, DVD Writer, Tape drive, etc to the Linux file system tree to allow the device to be accessed.
Most drives, etc are attached to the /mnt directory where /mnt is the 'mount point'.
Some Linux distributions mount memory cards and USB devices to a directory called /media. As the Linux file structure is a tree, you can add a mount point of your own anywhere you want (though it would possibly be in your /home directory somewhere.)
If you CD to the mount point you are effectively looking at the top level of the mounted media. If there's nothing mounted, you'll find a file called "lost & found" and possibly any files which were saved to the 'non-mounted' media in error.
Welcome to Linux Questions, hope that helps a bit.