Great software’s have been created by Nokia that makes it easy to update your Nokia phone. You must be wondering that why to update a phone, if it is working properly. This is actually a good question and as all the phones are different so I can't answer it for all the phones.
General update of a phone, adds new functions and features to it, makes it faster, on updating the software runs advanced applications or fixes security holes. So, the only information about firmware updates was that they will improve performance and functionality. The update updates the operating system of your phone which includes applications like the Calendar, the Messenger, the Contacts, etc.
P.S. - It is not possible to downgrade the firmware of your Nokia phone once it has been updated. Some applications and games from third-party developers might need to be installed again after updating the phone firmware. You can take a look at the extensive facts on the Nokia website.
How to update a Nokia Mobile Phone:
Step1: Download the Nokia PC Suite and backup all of the files on your phone. Simply start the Nokia PC Suite application and click on Backup button. Make sure you save everything and it may take some time.
Backup the contents of the Nokia phone as well. You find that option in Tools > Memory.
Step2: Download and install Nokia Software Updater app, to update the firmware of the phone. Make sure you connect the charger to your phone before you start the process because a failed update can brick your Nokia phone.
This is how you can upgrade your Nokia mobile phones.
So, go ahead and experience something new in your Nokia phones.