Here's a breakdown:
What it does:
* Expresses wishes or desires: "I wish I *were* taller." (instead of "was")
* Hypothetical situations: "If I *were* you, I wouldn't go." (instead of "was")
* Commands or suggestions: "I suggest that he *go* to the doctor." (instead of "goes")
* Expresses necessity or obligation: "It is important that you *be* there on time." (instead of "are")
How it differs from the indicative mood:
* The indicative mood describes facts or realities. It uses standard verb forms. For example: "He *is* happy."
* The subjunctive mood often uses a different verb form than the indicative, especially in the past tense and with the verb "to be". It can also use a different form of the present tense.
Examples:
* Wish: I wish I *were* a bird.
* Hypothetical: If I *were* rich, I would travel the world.
* Command: The teacher demanded that the students *be* quiet.
* Suggestion: She suggested that we *eat* out tonight.
Key points to remember:
* The subjunctive mood is less common in everyday speech than in formal writing.
* The subjunctive mood often appears in "that"-clauses.
* The form of the subjunctive verb can vary depending on the verb tense and the context.
If you're unsure whether to use the subjunctive mood, it's often helpful to consider the meaning of the sentence and whether you are expressing a wish, a hypothetical situation, a command, or a suggestion.