Centrifugal force is force that pulls rotating object away from the center of rotation, Centrifugal is part of Newtonian mechanics and it's derived from Newton's Second law $$F=ma$$
Where $F$ is force in newtons, $m$ is mass of an object and $a$ is acceleration. In circular motion acceleration is $a=\frac{v^2}{r}$ and full equation for centrifugal force is
$$
F=\frac{mv^2}{r}
$$
Where $v$ is speed and $r$ is radius. Here's sample image of circular motion and centrifugal force acting on an object:

![enter image description here][1]

Same happens with pilots of jet planes:

![enter image description here][2]

They experience centrifugal force and if that force is enough they can lost consciousness.

**EDIT:**

Imagine bus and someone who is standing in it, and suddenly bus driver turned bus, because car changed it's direction of velocity it has accelerated, When it has accelerated it changed it direction of velocity while someone who was standing was continuing moving in old direction, because of that he/she will fall, but because of bus driver is sitting very hardly he will experience centrifugal force. It's easier to imagine a spaceship, if he/she was floating relative to spaceship and spaceship has changed it direction of motion, it will accelerate, while he/she will be continuing moving in old direction so he/she won't experience centrifugal force while spaceship will. (I have found nice animation about that situation in spaceship [Click Here][3].)


  [1]: https://i.sstatic.net/tkd6z.jpg
  [2]: https://i.sstatic.net/HL9oT.gif
  [3]: http://labs.minutelabs.io/Relativistic-Space-Sheep/