The subjunctive is not a tense but a mood. Unlike the indicative, which is used to convey certainty, the subjunctive conveys doubt, desire or possibility, generally speaking. It has three forms in Spanish: the imperfect subjunctive, the present subjunctive and the future subjunctive, but that's only used in legal documents so you don't need to worry about that! Conjugating verbs into the subjunctive is not difficult to learn and will be covered soon enough. Present indicative sentence: No hay duda de que él es sinceroPresent subjunctive sentence: Dudo que él sea sinceroThe subjunctive is also used with verbs like querer and esperar and the conjunction queQuiero que visite a mi madre despues de mis vacaciones - I want to visit my mother after my holidayEspero que me hable ella - I hope that she speaks to meThe imperfect subjunctive denotes hypothetical desires, and has an equivalent in English. If I had the money I would buy a yacht - Si tuviera un dinero, yo compraría un yate