The simple past is used to talk about actions that started and finished in the past.
Key time expressions: yesterday, last night, two days ago, in 2000.
The past continuous is used to describe actions that were happening at a specific time in the past.
We often use it to show that one action was happening when another action interrupted it.
Example 1 (Simple Past): I watched a movie last night.
Example 2 (Past Continuous): I was watching a movie at 9 p.m.
Example 3 (Both tenses together): I was watching a movie when my friend called.