Capillary water is present in the capillary spaces and this water is easily available to plant roots.
Hygroscopic water is present as a thin film around soil particles and is not available to plant roots.
Gravitational water is the water that seeps down to the water table under the influence of gravity.
Chemically bound water is the water present in minerals and chemical compounds as their constituent.
Both gravitational and chemically bound water is not available to plants.