Vacuoles are simply just storage bins. They store things such as wastes and nutrients. A cell will break into a vacuole when what is inside is needed. If it contains waste, then it will simply hold on to it until it is able to rid itself of it.
Vacuoles act as containers.
A food vacuole in a single celled amoeba contains the food item that the amoeba has consumed. The central vacoule in a plant cell contains water and other substances. These substances could include such things as amino acids, sugars, and other compounds that the plant needs. The structure of a vacuole consists of a single membrane surrounding the liquid or solid contents inside. You people are annoying.