Linguistically, fadhail is plural from the word fadhilah which means virtue, and al-a'mal is plural from the word al-`amal which means action. Al-Fadhailul A'mal is related to the virtues of morality, not related to the provisions of halal-haram, or creed beliefs.
In matters of moral excellence, this can be in the form of performing sunnah prayers, increasing fasting, increasing dhikr, wirid, i'tikaf, and so on. Some of the practices of Al-Fadhailul A'mal are based on verses of the Qur'an, such as increasing the number of blessings because there is an order to pray for the Prophet, including the angels also pray for him; increase dhikr because there is an order to do dhikr as much as possible; alms priority orders; and many more. Al-Fadhailul A'mal is also based on the hadith of the Prophet Muhammad. in the hadith books.
While the basis is from the authentic and hasan hadith of the Prophet, Al-Fadhailul A'mal is not a subject of debate.