What is considered moderate to severe asthma compared to mild?

Asthma classificatio: Asthma is divided into categories based on a number of different things including symptoms and severity/frequency of symptoms, medications needed to relieve symptoms and frequency of their use, amount of decrease in pulmonary function among other things. So it's not just an easy answer. Generally, however, if only needing one rescue medication less than 1-2 times a week, considered to be mild.

Asthma: Forget about those subjective terms. Asthma is generally controllable, meaning absence of daily symptoms, absence of nocturnal symptoms, no restriction of normal activities, and rare use of medication for acute symptoms. If those criteria for control are not met, treatment should be increased to attain those criteria.