The square edge is unique for the up and down motion when slicing mostly vegetables or paper-thin meats. Also, used for scoring large blocks of ice at the bar.
Hand-wash with warm soapy water, rinse and dry with a cloth after each use. Blades should not be allowed to sit in water, especially after use with citrus and acidic foods as this may cause damage to the damascus blade.
Note, the blade should always be facing away from you.