Simple future (Future I)

The simple future (Future I) is used to express something in the future.

The simple future (Future I) refers to a future event, something that has not yet begun at the moment of speaking. It is often a predicion/prognosis or a statement of a future plan.

Simple future (Future I) vs present

The Simple future (Future I) has basically the same meaning as the present tense, when the latter is used with a future meaning. However, comparing the two tenses, the simple future expresses less certainty regarding the realization of the future event.  

When using the present tense with a future meaning, it is adviseable to use a word that determines the time that the event takes place i.e. future time.

The simple future (Future I) can also express an intention or a promise. In this case, the subject is, as a rule, in the 1st person singular or plural.

Furthermore, the simple future can be used to express a request/command. In this case, the subject is always in the 2nd person singular or plural or in the polite form. It is an alternative type of imperative.