A projectile is an object moving under the influence of gravity with a parabolic path. Its motion can be analyzed by separating the horizontal and vertical components. In the horizontal direction, the velocity is constant, while in the vertical direction there is a constant acceleration due to gravity. Projectile motion is used to model many real-world scenarios like thrown objects, diving, and artillery fire. Solving projectile motion problems involves separating the horizontal and vertical motions and using kinematic equations with the initial velocities and gravitational acceleration.