If you feel the need to thank your guardians, this is the ritual to use. When you use it you sacrifice an item (it has to be a consumable item) as a sign of appreciation to the guardians of the forest for what you conceive as a favour. Surviving a major battle or finally finding something to eat after days of starvation, might be good examples of this. Or just relief that your major frostbites are finally starting to heal.
Offerings: usually cooked foods, berries. Other foods could work, too, but the most numerous things we usually have is the cooked foods. Spoiled food items will make "you feel foolish". Poisonous food worked pre 3.51, not sure about now.
It can be used in place of the rituals that show gratitude for various action, but less effective than each specific ritual.