The wind never moves from high pressure to low pressure directly like a straight line, it is deflected because of the rotational movement of earth. The Coriolis force is the result of that motion.
1)In a register mark in 2 dimensions
Motion is a relative concept, it depends on the point of reference of it. We'll take the example of the turnstile seen in funfairs.
When Bernard throws the ball to Jacky(please forgive my lack of inspiration for those names, but well…), an observer placed outside the turnstile will see a straight trajectory for the ball's way.
But for Bernard and Jacky, Ball's trajectory will be deflected to the right in a curve's shape(So for everybody placed on the turnstile).
For earth it's almost the same idea, the turnstile symbolizes the rotating earth and ball's way represents wind's displacement(or current). For the southern hemisphere just resume the same pattern by reversing turnstile's rotation, the ball(the wind)will be deviated to the left.
2)In a three-dimensional register mark
The Coriolis force depends on three things: the mass of the moving body, its speed and its latitude. It can be written in that sentence:
Fc=2*m*(speed vector* angular speed vector)
The angular speed is the rotational earth speed(roughly 15 degrees per hour). Note that this equation mentions a vectors multiplication, to find vector's norm obtained the calculation is:
||speed vector||*||angular speed vector||*sin(L)
L is the moving thing(wind or current)'s latitude.
Notice: as the sine function is symmetrical relative to the point 0( in a Cartesian coordinating system)then we can deduce that the more the object is close to the latitude 0, the more Coriolis force decreases until it becomes zero at the equator. On the contrary, Coriolis force is strongest next to the poles.
There is a good illustration of this phenomenon with Foucault's pendulum(the first experiment had happened in the pantheon, there is one in Paris that runs continuously since 1995 I think…). I will do a little thing on it later it's pretty funny(we may guess our latitude depending on pendulum rotation speed).