Firmware

Unless otherwise stated, the jailbreak and unlock information report whether a device can be modified with publicly available software (read: no additional hardware required) if it was never jailbroken before. iTunes contacts ax.phobos.apple.com to check for updates.

Beware of scams that repackage freely available jailbreaks! Only use legit jailbreaks.

Apple TV

Apple TV firmwares have two different version and build numbers, which can lead to confusion when referencing them. As such, the internal build number is the best way to refer to a specific firmware.

The "Marketing"/"Displayed" columns are what is reported on the Apple TV's "About" screen
The "Internal" column refers to the ProductVersion and ProductBuildVersion keys in the IPSW's BuildManifest.plist