What is the difference between the past tenses?

In Spanish, there are 3 main past tenses.
Imperfect: Used when something happened over a long period of time, or when something used to happen habitually, or when someone "was doing" somethingeg - vivía en Inglaterra = I used to live in Englandcomía la cena cuando sonó el teléfono = I was eating dinner when the phone rang
Perfect: Used when something "has ____ed", and is formed from the present tense of haber and the past participle. eg - ya he ido al supermercado hoy = I have already gone to the supermarket today
Preterite: Used for a one-time or definitive action, and completed actions in the past. eg - fui al cine con mis amigos anteayer = the day before yesterday, I went to the cinema with my friends.