Welcome to HealingWell. If you are looking for some good info as an introduction to Asthma to understand your Mother's dx then check out this link as well as accompany your Mother to her Drs. visit to ask question. Knowledge is a wonderful thing.
http://www.mayoclinic.com/health/asthma/DS00021
Also read through the forum as you will see many threads that speak to Asthma.