Peace Offerings are things that you can give to other people. They differ from Gifts in that you can send a Peace Offering to anyone in the game (not just your friends), and that they cost favor points.
There are three Peace Offerings: A Pint of Ale, Flowers, and Energy Potions. A Pint of Ale and Flowers cost 5 Favor Points each. Energy Potions cost 10 Favor points. Considering that the Ale and flowers do not do anything, and the fact that you can get energy potions elsewhere, it is highly recommended to never give Peace Offerings.
It seems that the peace offerings were removed from the game but if you had any of the objects before they were removed you will still retain the items in the peace offerings section of your keep.