The words hubo and había are both used to express existence in the past. One in the preterite form and the other one in the imperfect form. We will see a few examples.
It is a simple preterite that expresses existence in the past and that is has been concluded.
Hubo un hombre en la guerra que no fue muerto.
There was a man in the war that was not killed.
En el concierto pasado hubo gran caos.
There was great chaos in the last concert.
No hubo ningún voluntario para repartir los volantes.
There wasn't any volunteer for the flyers delivery.
Hubo muchos problemas en la reunión.
There were many problems in the meeting.
It is an imperfect preterite that expresses existence in the past with no reference to the time it started or ended.
Cuando entré a mi cuarto, había una araña enorme.
When I went into my room there was a huge spider.
Había mucha nieve en la carretera.
There was a lot of snow on the road.
Había dos o tres personas en la sala de espera.
There were two or three people in the waiting room.
En el museo había muchas piedras arqueológicas.
There were many archeological artifacts in the museum.
Last night there was a storm. (preterite)
There will be another competition tomorrow. (future)
There will be five teams in the tournament. (future)
There would be more but one was cancelled. (conditional)
There was a volleyball game yesterday. (imperfect)
There were many spectators in the gym. (imperfect)
There were many of this group's fans here. (imperfect)
There were many children in the park. (imperfect)
You may hear some Spanish speakers conjugate Haber in plural;
Habían muchos niños en el parque. - There were many children in the park.
This use is incorrect. Regardless of the number of objects present in the sentence, Haber is always conjugated in the third-person singular when functioning as a verb meaning "there was/ there were".