Many off the rack suits have sleeves that are many inches too long. Ideally, you should allow 1/4″ to 1/2″ of shirt cuff (known as “linen”) to show when you rest your hands at your side.
Normally, pants on off the rack suits are unfinished and run about 38” long – too long for anyone to wear. You must have these hemmed.
Waist suppression is the descriptive term for the cinching of a jacket’s waist to accentuate the ideal “V” shape of the male torso. Many of the rack suits are rather boxy, so your tailor can rectify this by suppressing the waist of your jacket. When your tailor suppresses the waist, he helps the jacket hide whatever flaws you might have in order to make you appear that much closer to the masculine ideal.