What's the difference between 'por' y 'para'?

In spanish, there is a very big difference between those two words. Eventough they are both conectors, usually helpful to explain why someone did something or something happened, but their meaning differs a lot.

The first of them, 'por', is the one that is used to describe the reason, something that moves you into making that decision or what was the cause of something happening.

The second one, 'para', is used to describe the purpose, the final aim that you want to achieve by doing that action.