What is Islam and what are its Pillars?

It is reported in the sahih from Umar, may Allah be pleased with him, that the Messenger of Allah ﷺ said, “Islam is to testify that there is no deity worthy of worship in truth except Allah and that Muhammad is the Messenger of Allah, to establish the Salah (prayer), to give the Zakah (obligatory charity), to fast Ramadan, and to perform Hajj (pilgrimage) to the house of Allah if you have means to it.” This is the explanation of it (i.e., Islam) with regards to its pillars. And Islam is more comprehensive. It includes everything that Allah and His Messenger ﷺ commanded to do and abandoning everything that Allah and His Messenger ﷺ forbade, as Allah, the Exalted said, {Truly, the (only accepted) religion by Allah is Islam.} [Ali Imran, 19] However, these are its pillars. Some things are explained by their pillars, and (some) by all of their components. It is reported on the authority of Abu Hurayrah, may Allah be pleased with him, that the Prophet ﷺ said, “The Muslim is the one from whose tongue and hand the Muslims are safe.” This (hadith) indicates generality and that Islam encompasses the pillars and other (components). Therefore, a true Muslim is someone who fulfills the pillars (of Islam), what Allah has obligated upon him, and refrains from oppressing people and transgressing the boundaries of Allah. On the authority of Bahz Ibn Hakim who reported from his father, who from his grandfather said that he asked the Messenger of Allah ﷺ about Islam, so, he ﷺ replied, “(It is) that you submit your heart to Allah, turn your face towards Allah, pray the prescribed prayers, and offer the obligated zakah (charity).” Reported by Ahmad.