What is grammatical mood?
A grammatical mood is a type of sentence describing its purpose.
A grammatical mood is acategory which describes a purpose of the sentence. The moods can be:
indicative mood - the sentence informs about a fact Warsaw is a capital city of Poland.
imperative mood - the sentence gives other person a command or an order Open the book at page 10.
subjunctive mood - the sentence describes someone's wishes or assumptions In your place I would not do it this way.