Overall meaning:
ʿĀʾishah relates that the Messenger of Allah ﷺ would sit and recite the Quran while resting in her lap even though she was menstruating. This indicates that the body of a menstruating woman is pure and is not rendered impure by menstruation.

Points derived from the ḥadīth
1 – It is permissible to recite the Quran while reclining in the lap of a menstruating woman, for both her body and her clothes remain pure.
2 – The same report is taken by Ibn Daqīq al-ʿĪd to imply that a menstruating woman herself is forbidden to recite the Quran. He bases this on the assumption that, had it been lawful for her to recite, the question of purity would not have arisen in the first place.

A menstruating woman does not make up missed prayers but must make up missed fasts

Muʿādhah said: “I asked ʿĀʾishah, ‘Why is it that a menstruating woman makes up the fasts she missed yet does not make up the prayers?’ She replied, ‘Are you a Harūrī?’ I said, ‘I am not a Harūrī; I am only asking.’ She responded, ‘That used to befall us, and we were commanded to make up the fasts, but we were not commanded to make up the prayers.’” (1)

Explanation of unusual expressions:
“Are you a Harūrī?” – The term Harūrī refers to the town of Harūrāʾ near Kūfah. The first faction of the Khārijites that rebelled against ʿAlī ibn Abī Ṭālib emerged from there, and thus the Khārijites came to be known as Harūrīs.

Overall meaning:
Muʿādhah asked ʿĀʾishah for the reason why the Lawgiver obliges a menstruating woman to make up the days of fasting she missed during her period but does not require her to make up the prayers missed in that same time, even though both acts of worship are obligatory and, indeed, prayer is greater than fasting.