THE PRESENT and PAST SUBJUNCTIVE (le subjonctif présent et passé)
The subjunctive is what we call a 'mood'.
In French, it is usually found in dependent clauses introduced by 'que'. However, this does not mean that every time you come across a 'que', it will be followed by a subjunctive. The subjunctive is usually triggered by a main clause that contains an idea of will, desire, necessity, doubt, emotion or opinion. It can also be triggered by certain conjunctions.
The subjunctive mood is subdivided into four tenses. Two of them are hardly ever used, so you mainly need to focus on the present and the past tenses.
As far as the present is concerned, there is sometimes no difference between the indicative and subjunctive mood, since the subjunctive endings are -e, -es, -e, -ions, -iez, -ent (note that they are very close to those of the present tense for a lot of verbs), so you might not notice any difference (and, as explained below, it will probably make very little difference to your understanding).
When it comes to understanding and translating the subjunctive, you should quickly realise that, in most cases, it can be treated like verbs in the indicative mood. Obviously, you should endeavour to memorise the most common irregular forms (such as the verbs être, avoir, faire, pouvoir, vouloir, etc.)
In some cases, both the subjunctive and the indicative can be used and the choice of one over the other might suggest a nuance in the statement. For instance, if you consider the following statements
(1) Je cherche une maison qui est près de la plage.
(2) Je cherche une maison qui soit près de la plage.
In (1), you know that the house you're looking for exists while in (2) it is something you hope you'll find (it might exist or not).