speed stability
What has been stated above is true for both jet & prop airplanes at low speed where decreasing airspeed creates a greater drag rise than lift increase. It's known as the "back side of the power curve".
The difference in speed stability between jets & props is the effect of prop wash which varies the lift of the wing portion exposed to it, but most importantly varies the downward force created by the horizontal stabilizer.
This means that adding power tends to pitch the nose up, while decreasing power pitches nose down. In a well designed prop airplane the airspeed will remain very close to the trim speed with varying power settings mainly affecting vertical speed. On jets with engines mounted on/in the fuselage, power changes mainly affect airspeed with little pitch change.
The exceptions to this are low-wing jet aircraft with under-wing mounted engines like most large transports today. The low thrust line (below the cg) creates a pitching moment with thrust changes very similar to prop aircraft.
Pusher props and/or canards are different.