Even though we can’t see it, air is made of matter and will push back against an object moving through it. The force of air against an object is called air resistance, or drag. The faster an object goes, the greater the drag, since more air molecules are getting pushed out of the way.
The main forces acting on a parachute are gravity and drag. When you first release the parachute, the force of gravity pulls it downward, and the parachute speeds toward the ground. The faster the parachute falls, though, the more drag it creates. The drag force resists the downward movement of gravity, pushing the parachute back up.
As the parachute falls, the drag increases until it just balances out the pull of gravity. At that point, the parachute stops speeding up, and begins to fall at a steady speed. This steady speed is known as terminal velocity, the fastest something will go when pulled on by gravity in the presence of air resistance.