In the 1960s, the role of commentator was assigned at Mass as the reforms began to take root. Explaining the Mass was thought to be an important effort. Some music ministry leaders also endorsed a public presence, an animator, who encouraged participation. Continuing Chapter 2, section § II, we see a thought given to these purposes.
7. It is the celebrant’s responsibility to motivate the people in regard to this prayer by introductory comments on its liturgical and pastoral significance. Such an introduction, normally brief and addressed not to God but to the people, may touch on the liturgical season or on the theme of the feast or of the saint being celebrated, and it should connect these with the ensuing prayer. But an introduction may be omitted for a good reason, especially when the prayer of the faithful immediately follows the homily.
Commentary:
- An introduction is not a prayer as such, but a brief narrative addressed to the people present. Grammatically, God would be referred to in the third person, rather than the second.
- Brevity is important. There is a phenomenon of the “creeping” homily, where the presider offers multiple commentary at various points: the penitential act, readings, post-Communion, and here. Less is likely better.
- This portion of the Prayers of the Faithful remains optional. Today it seems universal, but I wonder what the experience of people would be if it were omitted.
Catholic Sensibility 
It mostly functions for the celebrant to cue the lector or deacon to proceed.