This is a subject within the realm of "temps verbals". You may want to do a Goggle search to find out more. Here is what I found:
In Catalan, there are three main tenses (in the indicative) that are used for events in the past: the imperfect, the preterite, and the perfect, see below.
Imperfect (pretèrit Imperfet) – when the event or state occurred continuously or repeatedly over a period of time. Anava al gimnàs cada dissabte. I went to the gym every Saturday.
Preterite (passat periphrastic) – when the event or state occurred at a point in time and it occurred in an interval which has ended and which does not include today. L'any passat vaig traslladar-me a Barcelona. Last year I moved to Barcelona.
Perfect (perfet o pretèrit Indefinit) – when the event or state occurred at a point in time and it occurred today or in an interval (week, month, year, etc.) which includes today. Avui m'he despertat a les sis. Today I woke up at six.
Hope it helps. Cheers!