How do you use the present subjunctive and what is it?

The present subjunctive is not a new tense. It is a version of the present tense which needs to be used in certain situations. The subjunctive is used to express doubt or desire.
To form the subjunctive, there are three simple steps. 1) Identify whether the infinitive version of the verb ends in -ar or -er/-ir.2) You must then use the stem of the present tense 'yo' form of the verb.3) Then, you have to add the -ar or -er/ir endings depending on whether the infinitive of the verb ends in -ar or -er/ier. The ONLY DIFFERENCE is that -ar verbs take -er/-ir verb endings, and vice versa.
FOR EXAMPLE: The verb HABLAR = TO TALK. This verb ends in 'ar'. (step 1)The present tense 'yo' form of hablar = hablo (step 2)In the present subjunctive, the yo form would therefore be 'hable' (step 3)
The Present Subjunctive conjugations of HABLAR would therefore be;Yo Hable Tu HablesEl Hable Nosotros Hablemos Vosotros HableisEllos Hablen
The Present Subjunctive conjugations for an -er/-ir verb ending therefore would be;Yo coma Tu comas El coma Nosotros comamos Vosotros Comais Ellos Coman
In Practise:Megan wants Elizabeth to wash the dishes = Megan quiere que Elizabeth LAVE los platos I hope we can eat pizza tonight = Espero que podamos comer pizza anoche.