Grammatical mood (sometimes called 'mode') is a way of categorising the attitude reflected in the way a verb is used.
In Spanish there are three or four moods depending on how one prefers to classify them:
- Indicative - used for facts and real situations
- Imperative - used for commands and requests
- Conditional* - used for something contingent upon something else
- Subjunctive - used for subjective and hypothetical events or situations
* Spanish linguists tend to classify the conditional as a tense for technical reasons to do with how it evolved from Latin. However, we prefer to classify it as a mood since this is closer to how it works, it is more consistent with French, and it preserves the concept of tense as being temporal. (It's not clear where one could draw something conditional on a timeline.)