Porifera means" pore-bearing" ; their sac-like bodies are perforated by many pores.
They have true tissues & no organ ; cells are somewhat independent.
Water is drawn through the pores (ostia) into a central cavity (spongocoel), then flow out of the sponge through a larger opening called the osculum.
Their body is a mass of cells embedded in gelatinous matrix and stiffened by spicules of calcium carbonate or silica&collagen.