Indicative: The first president of the United states was George Washington. The indicative form is used to express simple statements.
Imperative: Pick up all of your dirty clothes off the floor right now!. Write a thank you letter to your grandmother for your birthday gift. The imperative form is used to give orders.
Conditional: If I had enough money, I would travel around the world. The conditional form is used to express a wish or a situation that depends on another.
Subjunctive: I wish rotary phones were still in use. The subjunctive is used to express a wish or a hypothetical situation.