flutter is when all or one the control surfaces (alieron/elevator/rudder) vibrates really fast. usually because the plane is going to fast. but can also be caused by improper setup.

gasser. their are 2 definitions
in the forums its usually a gasoline powered plane (engine similir to that of a weed wacker)
some use the term for when refering to any "wet" (nitro/diesel/gasoline) powered plane

as for that plane. some like it some hate it. its not really a "trainer" so to speak
i would train on a traditional trainer. then move up to one of those later. (dont buy it yet)