According to my SIL, this treatment helps to open the bronchi, which are the airways of the lungs. The medicine relaxes the muscles around the airways. It is an aerosol and is given to through an aerosol machine (nebulizer).
I remembered when he was about 4-5 months old, he was on this nebulizer as well. It is kind of painful to see him suffering at this young age. However, I must praise him for being so obedient & clever. Hence, my younger brother & I decided to reward him with the Thomas & Friends Road & Rail set.