"To reset the device" means to restore it back to its original settings, which can help fix any issues or problems it might be experiencing. It's like giving the device a fresh start. Full definition
Always remember to factory reset your device before you change or upgrade to a new smartphone. (phoneradar.com)
Assuming you don't have the easy option to reset the device using one of the tricks above, you should probably give up on the data stored on your device. (howtogeek.com)
It will also reset your device back to factory settings. (mobilesyrup.com)