Every verb in Latin has mood, that is, it expresses a certain modality of action.  There are three moods for the Latin verb, not including the infinitive, which does not have mood or person or number (hence, its name which means "not defined":  in = not, finite = defined).  The most familiar mood is the indicative.  This is used to express facts, to make statements, or to ask simple questions of fact.  It is the same as just about every English verb you use, since English does not really have much of a mood structure any more.  The second most familiar mood is the imperative.   This is used to give orders or commands.  The imperative directly expresses an action as a function of the speaker's will, desire, authority, and so on.  Compare:  "You are going to the store." which is a simple statement of fact and which uses the indicative with the command "Go to the store!" which has all the same components as the indicative statement (it is addressed to an unexpressed "you"; it deals with the action of "going"; and the end of the going is the same, "to the store"). BUT, in the command all these aspects of the action are directly embedded in the speakers will and desire.  The third and, for English speakers, the least familiar mood, is the subjunctive.  It has three independent uses:   It may be used to give direct commands (jussive subjunctive).   It may be used to express potential (potential subjunctive).   And it may be used to express direct wishes, prayers, and fears (optative subjunctive).