Stuffing is the soft material inside pillows, mattresses, or sofa cushions. Without stuffing, your comfy chair wouldn't be very comfy.
Stuffing is meant either to make things more comfortable, or more delicious. The edible kind of stuffing is a savory filling that's stuffed inside something being cooked, like a turkey or a potato. Stuffing stems from the verb stuff, which meant "fill the belly with food and drink" in the early 1400s, and came to mean "fill the interior of a pastry or the cavity of a fowl or beast" later in the century.