! n00b question alert !

My computer has only 1 hard drive with sda1 as root, sda2 as swap and sda3 as home. I have an external usb drive for storage. I store my Clonezilla images on this external usb drive.

I used Clonezilla twice to image my ubuntu partition (sda1). The first time, I had Clonezilla create an "image" file. It resulted in one folder ending "img" (no period in folder name). The second time, I had Clonezilla create a "recovery" file. It resulted in one iso file ending ".iso" (has period in file name).

My questions:

1) What is the difference? I thought all images were iso. Obviously I was wrong.
2) Assume I burn each image to its separate CD / DVD. Assume later something bad happens and I need to re-install everything on sda1. Instead of going through the time to re-install the OS and do all the synaptic updates, could I install one of these images? If yes, then which image?

Thank you!

1) img is just a partition image. You can burn this to a CD, but you will still need to run Clonezilla separately to restore the image. While the iso is a bootable CD image which has clonezilla live built-in, so you can boot off the CD & run clonezilla directly.

2) If you only backup sda1, it will help you recover that partition's data. (eg. you screw-up what's inside sda1) It will not help if; your hdd dies; your partition table corrupts; sda3 screw-up.
So if want the ability to restore a full working OS from the backup, you will need to backup the whole disk (sda), not just sda1.

As for which image, if you use img, you will need to boot clozilla live from either another CD or USB drive. if you use the iso image, you will have Clonezilla Live and your image in the same CD/DVD.