For those interested in the background of this question, it's almost certainly form Ray Wenderlich's Sprite Kit Tutorial for Beginners. Search that link for the heading "Shooting Projectiles"
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In terms of the situations where a point can be considered a vector, it can if the other end of the vector is implicit rather than explicit.
In this particular case, the point is being treated as a vector from the origin (0,0)
to the point given.
So the actual vector calculation is (you appear to have the points reversed by the way):
(0,0)->(10,3) - (0,0)->(1,4) = (0,0)->(9,-1)