The indicative mood indicates facts or ideas. For example:
John is walking down the street.
Mary is a good student.
The book that Bill was seeking is on the table.
Notice that these sentences are simply stating facts. Each of these verbs is in the indicative mood.
The imperative mood gives commands. For example:
Hand me that book.
Go to the store.
Stand up.
Notice that each of these sentences is making a request. Without more contextual information, it is impossible to tell the strength with which these commands are given. Not all verbs in the imperative mood are forceful commands, although they can be. Without more information, some writers use an exclamation point to imply the forcefulness of a command. For example:
Hand me that book!
Go to the store!
Stand up!
The exclamation point only implies that the command is desired immediately, not that there is any anger intended in the command.
The subjunctive conveys a theoretical, ideal, or wishful situation. For example:
Were I your husband, I would love you.
Let the buyer beware.
The teacher insisted that we all pass the exam.
Notice that in each case, the action conveyed by the verb has not actually happened but is one that is wished for or implies a theoretical or ideal situation. Notice that in the first sentence, the verb “were” is used although it refers to the singular pronoun “I.” This is a telltale sign of the subjunctive in English. The sentence:
Was I your husband, I would love you.
is grammatically incorrect.