Fictional forces are forces that appear to act on an object in a non-inertial reference frame, where the observer is accelerating. These forces are not caused by any physical interaction but are perceived due to the acceleration of the frame itself. Common examples include the centrifugal force felt when turning in a car or the Coriolis effect observed in rotating systems. In physics, fictional forces help explain the motion of objects from the perspective of an accelerating observer. They allow for the application of Newton's laws of motion in non-inertial frames, making it easier to analyze situations like roller coasters or spacecraft maneuvering in orbit.