Question

what is projectile

Answer 1

An object that's been launched with some initial velocity in some direction.

Answer 2

To further expand upon Jemurray3's answer, a projectile, once launched with initial velocity, has no other forces acting upon it except for gravity in the negative y direction. Therefore, \[\begin{matrix}\sum F_x = 0 \\ \sum F_y = mg\end{matrix}\]This leads to several simplifications to the equations of motion. These equations can be found here: http://en.wikipedia.org/wiki/Projectile_motion

Answer 3

I would be careful ... though I would assume based on the question that you are correct in the context of shweta's question, those conditions are applicable only to an object in free fall. A projectile may experience drag, in which case those conditions are no longer valid. :)