Buprenorphine is a opioid partial agonist, which means that it can produce the typical opioid effects and side effects, however, its maximal effects are less than those of full agonists.  Buprenorphine also allows suppression of withdrawal symptoms and decreases cravings, but for a longer time (about 24-60 hours) after each dose.  Because of its partial agonist activity, it is safer in overdose and carries lower risk of side effects.