What baseband version does my iPhone have?
The baseband refers to the part of your iPhone that handles communications with a cellular network, namely a cellular modem running its own firmware. You may need to look up your baseband version to see if you're running the latest update or to help with unlocking your iPhone. Apple often updates the baseband as part of larger iOS firmware updates.
To find your current baseband version:
Navigate to Settings -> General -> About -> Modem Firmware