Projectile motion is simply the motion of a projectile. Any mass that is moving in the atmosphere after being thrown is in projectile motion. A thrown baseball is a projectile after it leaves the thrower's hand. The same is true for footballs, basketballs, volleyballs, soccer balls, and golf balls, as well as bullets, arrows, and dropped dumb bombs. Smart bombs with their own guidance systems will not necessarily follow the rules of projectile motion.
A projectile is influenced mainly by the acceleration due to gravity, however other forces may act upon it. The atmosphere has a certain effect upon a projectile.
Projectile motion is rather easy to study if we ignore the effects of the atmosphere and the rotation and curvature of the Earth.
Projectile motion is a form of two dimensional motion in a vertical plane.
A thrown object will follow a parabolic path.
Projectile motion can best be studied by separating the vertical motion from the horizontal motion. The vertical motion is effected by the acceleration due to gravity.