What is velocity?
Velocity is the speed and direction of motion of an object.
Velocity is a vector quantity of motion in that it has magnitude, or speed, and direction.
To change an object's direction of motion requires a change in velocity direction which requires an external force.
To change an object's speed requires a change in the magnitude of its velocity which requires an external force.
Newtons laws state that in the absence of an external force an object moves in a straight line at constant speed. Newton describes gravity as a force.
Einstein describes gravity as the curvature of spacetime which means that it is not a force. Objects moving in the absence of an external force, which includes motion under gravity, follow a geodesic which is the 4 dimensional equivalent of a straight line.
Another way of looking at velocity is to consider a moving object's momentum. Momentum is the object's mass multiplied by its velocity