On the twenty-fifth day of Kislev, the building of the Mishkan was completed. On that very same day, hundreds of years later, the Bais Hamikdosh was rededicated by the Chashmonaim after the defilement of the Greeks, and the miracle of the oil occurred. The eight days beginning from the twenty-fifth of Kislev were, therefore, designated by our Sages as days of praise and thanksgiving and they enacted the mitzvah of kindling lights on each evening of this eight-day period—in order to publicize the miracle.
The kindling of the Chanukah lights is the only area of halachah in which the Talmud singles out different levels of observance (e.g. mehadrin, mehadrin min hamehadrin). The purpose of this work is to facilitate this observance.