what does scheduled aircraft and non scheduled aircraft mean?

Answer 1

It can mean that the airline has a certain type of plane they use from point a to point b. For some reason they has to change the plane to some thing else.
Some people like to fly only on certain types of aircraft, and book a flight according to what is being used.

It can be a charter airline.

Another meaning can be that an airline during certain very busy weeks well add another flight between 2 cities. Which is not normally scheduled.

And last it can apply to Tour or flight seeing flights that do not leave at a fix time, they can depart and land when ever. Normally at small airports/

Answer 2

Scheduled aircrafty are planes that have timetable for arrivals and departure, forecasted way in advance.

Non-scheduled flights are ad-hoc flights that are being flown at short notice, like chartered flights, military flights and light aircraft flights.

Answer 3

scheduled are usually more expensive as they must fly at a certain time, non-scheduled are more likely to be delayed and given low priority if a flight needs moving..