In a cell, a food vacuole is a membrane-surrounded structure that stores food temporarily until the organism needs it. Another type of vacuole is very similar, but it stores waste products until they can be eliminated from the cell.
While both plant and animal cells have vacuoles, plants usually have larger vacuoles. A plant vacuole helps add structure and stiffness to the plant. Once a plant stops growing, the vacuole may expand to take up more than half the space in the cell. It's also a good storage place for water. When plants wilt, it's often because the water is being depleted from vacuoles. If the wilting is only due to lack of water, the plant perks up and retains its structure when it is watered.