What is the different between the preterite and imperfect tense?

Conjugation is not as common in English as it is in Spanish, especially in the past tense. Unlike English, there are two versions of the Spanish past tense called the Preterite and Imperfect tense, each with a unique set of endings. It can be difficult to determine when to use each but there are a set of general rules to follow which make it much easier. As a rule of thumb: the preterite is used when referring to actions that were completed in the past, actions with a definite beginning and definite end. The imperfect has a less specific time frame, and talks about things you were doing at some point in time or that you used to do. Here is a more concrete example. Take the three past forms of the English verb "to work" - "I worked", "I was working", and "I used to work". In Spanish, the preterite is almost always used with the first option, "I worked". The latter two, "I was working" and "I used to work" are usually conjugated in the imperfect form. There are also certain temporal phrases that, if memorised, will help you determine whether or not to use the preterite or imperfect. Phrases such as "ayer", "anoche", and "hace dos dias" hint towards the preterite, and phrases such as "a menudo", "siempre", and "a veces" hint towards the imperfect.