Stability is a measure of a vessels ability to remain upright and to return to this position when heeled.
Small angle stability is a measure of a vessels stability characteristics to angles of no more than 10 degree's. The assumption is made within this range that the increased bouyancy from the further submerged side of a heeled vessel will be equal to the lost bouyancy on the opposing side.
Large angle stability considers the vessels righting moment from an upright position to the angle of vanishing stability.
Dynamic stability examines the effects of wind, waves, and cargo handling to ensure sufficient righting energy to return the vessel to upright.