Bad mood, happy mood, gloomy mood these are emotions. When one uses the word mood in reference to grammar we describe the attitude of the speaker about what he or she is saying. There are three moods in both English and Latin. The indicative is the most common and does what it says. It indicates or expresses facts.
Most common speech is in the indicative mood.
The subjunctive mood is less common in English than in other languages. It expresses an action that is a wish, hope, uncertainty or other attitude towards a fact. In Latin the subjunctive is always subjective to the main verb.