Projectile is the name given to a body thrown with some initial velocity with the horizontal direction, and then allowed to move in two dimensions under the action of gravity alone, without being propelled by any engine or fuel.
After projection, the object will move under the combined effect of two independent perpendicular velocities.
(i) Horizontal velocity, which remains constant throughout the motion (neglecting the air friction).
(ii) Vertical velocity which increases due to gravity. Initial value of this velocity at origin is zero.