PAST TENSES

finished action in the past

it's mentioned WHEN (yesterday, last week, two years ago...) or it's understandable from the context

verbs in past form (regular -ed, irregular)

example: "I went shopping yesterday." "She watched this movie last weekend."

usually used in storytelling, when we want to say something WAS HAPPENING (p. continuous) and then something HAPPENED (p. simple) which interrupted this action

WAS/WERE + VERB -ING

example: "I was watching the TV, when my brother broke a glass." "I called my friend while I was packing my stuff for the trip."

used in storytelling, if one action happened BEFORE the other (deeper in the past)

HAD + past participle (verb in 3rd form)

example: "I couldn't get into my flat, because I HAD LOST the keys." (You lost the keys first and then you couldn't unlock the door)