An exempt carrier hauls freight that falls outside some of the usual federal economic regulations — typically because of the commodity involved (classic examples are unprocessed agricultural products) or the specific kind of movement. The exemption is about certain economic rules, not a free pass on safety.
Even when exempt from those requirements, carriers still have to meet safety standards under the FMCSA. The distinction mainly affects which authority and rules apply, compared with a standard for-hire authorized carrier.