Mood

There are 3 moods in English, the indicative mood, the imperative mood, and the subjunctive mood.
The indicative mood is used to make statements and to ask questions. Most of the verbs that you commonly use are in the indicative mood.

The secretary wrote the letter. (statement or fact)
Did you buy this dress? (question)

The imperative mood is used to express a comand or a request. The imperative mood is found only in the present tense, second person. The subject is always the pronoun you which is seldom expressed.

Come here at once! (command)
Close the window, Mike. (request)

The subjenctive mood is used to express a wish or a condition which is contrary to fact.

If he were here, I would tell him the news. (He is not here)
I wish I were in America. (express a wishes)