If hypothethically a car tries to go in two different directions at the same time, which direction will it end up going? When we add two vectors(A and B), we get one resultant sum vector(C).
i.e. adding two different directions gives us one resultant direction.
So in the same way if a hypothetical car was trying to go in two different directions at the same time somehow , can the direction it will end up going  be figured out by simply adding up those two directions(the two vectors)?

 A: I'm confused as to how exactly the car is trying to go in two different directions; maybe its wheels are misaligned? In that case, it will experience forces in two different directions.
You can then take the vector resultant of the forces to get a net force, and the car will be accelerated in that direction.
A: In place of a car I am going to give you an example of an electron .
Suppose there is an electron going in the positive X direction with some speed $v$ . It enters a region of uniform magnetic field whose direction is into the plane of this screen ( as shown in fig)

From Lorentz force formula , we know that the electron will experience a force perpendicular to the direction of its velocity. The electron will start following a curved path . Same is true with a ball tied with a string and rotated in a circular motion

The electron and the ball used in the above examples followed a curved path which is due to the resultant direction . So we saw that if something is given speed in two directions it always go on their resultant direction.
