Cisco IOS-XE, can someone explain the output of show platform command?

Hi, What's the difference between the "Software Version" and "Firmware Version"?

FYI the device was downgraded from 16.12.1a to 16.08.01a in order to comply with our customer's security policy.

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#show platform Slot CPLD Version Software Version Firmware Version --------- ------------------- ----------------------- ------------------------ 1 07091401 16.08.01a 16.12.01a 2 07062111 16.08.01a 16.12.01a 3 07051680 16.08.01a 16.12.01a