I think the confusion is more general. About what those two forces are:
When a truck is going around a curve at constant speed, its velocity is changing. Velocity is speed and direction. Therefore direction changing... is velocity changing. Changing velocity is acceleration.
So, it takes acceleration to move along a curve. By $F=ma$, that takes force. That’s called centripetal force, the force to keep something turning (and eventually revolving around a center-point ). Centripetal force points in the direction of velocity change: toward the center. The force needed to keep the truck turning is toward the center of curvature. The force comes from friction. That’s why if it was slippery the truck would slide outward, away from that center of revolution, from the center of the curve. If slippery, there’d be insufficient centripetal force to keep it turning. That’s all from a still frame.
If you’re in the truck, you feel a force pulling you away from the center (relative to the truck), as if there is extra gravity. The truck is an “inertial reference frame” and is accelerating (turning). The apparent force felt by things in the revolving frame is called centrifugal force and it is directly outward. So if something in the frame of the truck is slung outward, THAT force slinging it.. is centrigul force.