Here's why:

* Gravity: When an object falls, gravity pulls it downward, causing it to accelerate.

* Air Resistance: As the object falls faster, it encounters more air resistance (drag). Air resistance is a force that opposes the object's motion.

* Terminal Velocity: At a certain speed, the force of air resistance becomes equal and opposite to the force of gravity. This means the net force on the object is zero, and it stops accelerating. The object continues to fall at this constant speed, which is called terminal velocity.

Important Note: Terminal velocity depends on factors like the object's shape, mass, and the density of the air.