Tense
Tense is the grammatical term that refers to the time when the action of the verb occurs: past, present, future. The time frame of an action is usually established by referring to the present moment; for example, the preterit and the future are respectively past and future in relation to the present.
However, some tenses establish their time frame by referring to other actions in the past or in the future. For example, the pluperfect tense indicates a past action that occurred prior to the the completion of another past action. Actions that occur before another action are described as being anterior.
Tenses are also described by their number of parts. For example, a tense with only one verb form is called a simple tense (ie, the preterit). In contrast, a tense comprising two forms, the auxiliary verb and the participle, is referred to as a compound tense (ie, the present perfect).
Aspect
Aspect, unlike tense, is not concerned with placing events on a time line. Rather, aspect is concerned with making distinctions about the kinds of actions that are described by verbs: progressive actions, punctual actions, habitual actions, etc.
The most important aspectual distinction in Spanish concerns the difference between the two most common past tenses: the imperfect and the preterit. While both tenses refer to actions in the past, they are used for very different types of actions. The imperfect indicates an action that is ongoing or habitual. Actions in the imperfect may be simultaneous or overlapping. The preterit on the other hand, indicates an action that is in a strict sequence in relation to another action. In other words, an event in the preterit must be completed before another may be used in narration.
These aspectual differences are best understood in a narrative context where the imperfect is typically used to set the scene of a story by giving background information.
Every October there was a huge pilgrimage. In the whole highway, I think there were twelve lanes, there were no cars, just, the carriage where the doll went.
The preterit is used for the foreground, that is, the plotline events. Note that plot line events are sequential, that is, an event must be completed before another event begins.
A los diez años nos volvimos a Buenos Aires, Argentina. Y claro nos fuimos en barco, cuando volvimos a Buenos Aires nos fuimos a Houston, ahí en Galveston…After ten years we went back to Buenos Aires, Argentina. And of course we went by boat, when we went back to Buenos Aires we went to Houston, there in Galveston…
For more information about the different uses of imperfect versus preterit see also the page about narration.
Mood
Mood is a grammatical category distinguishing verb tenses. There are three moods in Spanish: indicative, subjunctive, and imperative. All of these moods, except the imperative, may be conjugated in different tenses. Each of these moods has a different function.
The indicative mood is the most common and is used to relate facts and objective statements.
Cada domingo voy a Reynosa con mi mamá y con mi papá.Every Sunday I go to Reynosa with my mom and with my dad.
The subjunctive mood is used more commonly in Spanish than in English. It is used to express reactions and feelings (subjective thoughts).
Espero que el español se vuelva tal vez otro idioma oficial de los Estados Unidos.I hope that maybe Spanish becomes another official language in the United States.
The imperative mood is used to give direct orders or commands.
Oye y cuéntanos, ¿cómo era vivir en México?Listen, tell us, how was living in Mexico like?
Voice
Voice is a grammatical category describing the relationship between a verb and its subject. Voice is either active or passive. Active voice refers to the situation where the subject of the sentence performs the action of the verb.
Mi papá mudaba todas las cosas.My dad moved all the things.
On the other hand, passive voice refers to the situation where the subject receives the action of the verb.
Todas las cosas eran mudadas por mi padre. All the things were moved by my dad.