Bronchodilators relieve the symptoms of asthma by relaxing the muscles that can tighten around the airways. This helps to open up the airways.
Short-acting bronchodilator inhalers are often referred to as rescue inhalers and are used to quickly relieve the cough, wheeze, chest tightness, and shortness of breath caused by asthma. They may also be used prior to exercise for people with exercise-induced asthma. These should not be used daily in the routine treatment of asthma. If you need to use a short-acting bronchodilator as a rescue inhaler more than twice a week, then your asthma is not optimally controlled. Ask your doctor about improving your asthma controller medication.
Long-acting bronchodilators are sometimes used in combination with inhaled steroids for control of asthma symptoms or when someone has ongoing asthma symptoms despite treatment with a daily inhaled steroid. Long-acting bronchodilators are never used alone as long-term therapy for asthma.
For in-depth information, see WebMD's article on Bronchodilators: Airway Openers.