Transmission

That is a mechanical linkage. The shifter moves a lever at the bottom of the steering column, that moves a rod which connects to a bell-crank which in turn moves the lever on the transmission. If the bushings go bad or the retaining pins fail the linkage can become very loose. If the transmission side has an issue you get the same results.

Open the hood, set the parking brake or have someone step on the brake and move the shift lever. Anything that is wrong should become readily apparent. The linkage should move as one, with just a small amount of slop to allow for engine motion.