Larah, as Vinicius and Chris pointed out, when you talk about events in the past, there are multiple situations that can come up:
1) something that started in the past and has ended
2) something that started in the past and is still relevant
3) something that was going on in the past when something else happened
Each of these situations uses a different verb construction. As Chris mentions, the explanation of the verb tenses can get a bit involved and grammar books take many pages to explain all the options.