Usage of Indicative
The indicative mode is used wherever the real can be expressed. There is no room for doubt or uncertainty. For this, we prefer to use the conditional or the subjunctive.
There are four simple tenses to the indicative (the present, the imperfect, the simple past and the simple future) and four compound tenses (present perfect, past perfect, past perfect and past future) which allow us to express current actions, past actions or future actions.
The indicative is the tense that makes it possible to grasp the facts, the acts, the opinions or the thoughts in their realization. This is by far the most used mode in the needs of the current conversation. It is also the mode of negative and interrogative sentences.
Even in a subordinate proposition after "que", we can find the indicative if it is a certain action. As soon as we introduce the doubt or the notion of probability, we use the subjunctive. The following example illustrates this:
il est probable qu'il viendra. (indicative)
il est possible qu'il vienne. (subjunctive)
Note however that in the spoken language, we use more and more the subjunctive after the "que" which is not necessarily right since the action is already completed so real.
We can also note that when a proposition is completely false or unreal and that this leaves no more doubt, we use the indicative again to express a reality: Il s'est mis en tête qu'elle viendra le voir.