A metered-dose inhaler lets you breathe the medicine into your lungs quickly. Inhaled medicine works faster than the same medicine in a pill. An inhaler allows you to take less medicine than you would need if you took it as a pill. These inhalers are commonly used to deliver albuterol to patients with breathing problems. 

Please watch the below video on how to use a pressurized metered-dose inhaler.  

Reference-https://www.healthwise.net/rxhealth/Content/StdDocument.aspx?DOCHWID=ud1565