In French, the subjunctive is a "mood" (conjugation of a verb) which is used when expressing wish, hope, fear, uncertainty or other attitudes and feelings towards something. You should try to use the subjunctive in essays as it is seen as a more complex grammar point. There are several phrases which require the subjunctive after the "trigger word", such as: "il faut que", "je veux que", "je suis contente que" etc. Here you can see that the trigger usually ends with "que" which can act as a hint for knowing when to use the subjunctive. However, something to note is that there has to be two different people doing the action, or an expression requesting that one particular person does something. For instance, the subjunctive would not be required when saying "je veux que je fais la vaisselle", because there is only one person involved. However if it was "je veux que tu fasses la vaisselle", you can see that the subjunctive is used "fasses" because there are two different people involved.