You can use a Bonus Action to speak this magic sword's Command Word, causing flames to erupt from the blade. These flames shed bright light in a 40-foot radius and dim light for an additional 40 feet. While the sword is ablaze, it deals an extra 2d6 fire damage to any target it hits. The flames last until you use a Bonus Action to speak the Command Word again or until you drop or sheathe the sword.
This sword deals magic damage (slashing), with hit dice corresponding to the type of sword it is. (1d12 for Great Sword, 1d6 for Short Sword, etc.) and deals an additional 2d6 Fire damage when activated with the command word.
The Flame Tongue longsword owned by Riff Ramone also has Magic Aura Detection, which allows the user to cast Detect Magic once a day, and reveals its school of magic in greater detail than the usual Detect Magic spell.