Explain to those knowing only of the Ordinary Form of Mass, what incense is and why it is used during the Liturgy at Mass? In the Mass of Paul VI (OF = Ordinary Form) it is extremely rare throughout a liturgical year for incense to be used as compared to what is now the EF = Extraordinary Form of the Mass.

Explain to say one's children who know of only the Ordinary Form of Mass, what incense is and why it is used at Mass?

The questions are: what is incense, when and why is it used in either form of the Mass, are there rubrics in the Missal determining its use in either form of the Mass? What dictated the differences in its use from the EF to the OF of the Mass?  



cf. Holy Smoke - The Use of Incense in the Catholic Church
Incense as used in Christian rites, including the office of readings, as well as the Mass, is a sensory manifestation of the prayers of the faithful rising to God, as mentioned in Psalms, particularly 141:2 (RSVCE) and Revelations 5:8 (RSVCE).

This is probably more a matter of style than anything else. The incense ceremonies take time, and my own sense is that among those who favor the Ordinary Form, that what the use of incense adds to a celebration of the mass is not worth the time it takes to complete the ceremonies, while those with a preference of the Extraordinary Form are more tolerant of the time it takes, and willing to practice the patience required to attain the benefits they remember. To my knowledge nothing in the Rubrics that mandates the reduction of the role of incense in the Ordinary form, but this is not my primary area of expertise.



Please see  Incensation, 276 &amp; 277 |  IV. SOME GENERAL NORMS FOR ALL FORMS OF MASS | GENERAL INSTRUCTION OF THE ROMAN MISSAL