$A$ particle is projected in air at some angle to the horizontal and moves along a parabola as shown in the figure,where $x$ and $y$ indicate horizontal and vertical directions,respectively. The diagram shows the direction of velocity and acceleration at points $A$,$B$,and $C$.

(N/A) $v_{x} = \text{Horizontal component of velocity} = v \cos \theta = \text{constant}$
$v_{y} = \text{Vertical component of velocity} = v \sin \theta$
Velocity is always tangential to the curve in the direction of motion,and acceleration is always vertically downward and equal to $g$.