How to easily make a complete backup of your Android system partitions
Tap the Wrench icon to get some settings sorted out before proceeding. First, choose a place to store your backups - that is, choose whether it will be your device's internal memory, or external SD card storage. The second choice makes more sense if you have a big capacity microSD card inside, but it's up to you. The second option - Backup Formats - goes as follows. Choose tar for Samsung devices. Choose img if you will be restoring through Fastboot commands. Or choose tar.gz if you have any other smartphone and would like to keep a sufficiently well compressed copy of your partitions around.
Now that you are all set-up, press the back softkey to go back to the partition list, and choose which ones you want to backup. When you're done, press the circular blue Download button to begin the backup process. You have a chance to proceed or cancel, so take a deep breathe, and press Backup when you're ready to get done with this thing. The process could take a while, depending on how many partitions you'll be archiving, so be patient. There isn't much room for screw-ups, so worry not. When the process ends successfully, you'll get a toast notification and you'll be happy to know you've got a reliable backup in those critical moments when an experiment goes awry.