It's all relative. Most airlines have a "full" coach fare, usually designated "Y", and a variety of lower fares (common designations are "K", "Q", "U", "L") all referred to as "discounted". The lower fares usually have various restrictions such as being non-refundable or requiring a Saturday night within the itinerary. Some lower fares last only for a few days or when a limited number of seats per plane sold at that fare are gone.
"Usually it is better to wait for a fare war rather than buy at their everyday low price."