hubo and había !
What is the difference between these words? when we use each of them?
It's the difference between the preterite and imperfect tense: http://studyspanish.com/lessons/pretimp1.htm
the preterite is used for completed actions that happened at a specific time in the past. (hubo)
the imperfect is used for incomplete actions that are not seen as completed. (había)
I've been trying to sort out the two myself and it's pretty confusing.
Hubo is used for one-time events, like an accident or an explosion. Habia is for ongoing situations.