What is the difference between "ser" and "estar"?

The difference between these two verbs is best shown by examples.

Ser: It is used in the following context for the word being: "La manzana es verde" (The apple is green) This shows that "ser" has more to do with characteristics of the object that about conditions, which is what "estar" is about.

Estar: Used in this context: "La manzana está mala". As it is used here it is clear that it is referring to the condition of the apple not about its appearance or characteristics.