All praise is due to Allah. May peace and blessings be upon the Last Prophet. Allah, the Exalted, states, This day, I have perfected your religion for you, completed My Favour upon you, and have chosen for you Islâm as your religion. Allah (Glorified be He) also says: Truly, the religion with Allâh is Islâm. Allah (Glorified be He) also says: And whoever seeks a religion other than Islâm, it will never be accepted of him, and in the Hereafter he will be one of the losers.
Islam is to submit to Allah by Tawhid (belief in the Oneness of Allah/monotheism), yielding to Him by obedience and leaving acts of Shirk (associating others with Allah in His Divinity or worship) and those who commit Shirk. Shirk was the belief of the Arabs before the advent of the Da`wah (calling to Islam) of Muhammad (peace be upon him).
It is narrated by AlBukhari that Abu Rajaa' Al`Utaridi said, we used to worship a certain stone, but if we found a better stone, we would throw the first stone away and worship the other one. If we did not find any stone to worship, we would grasp a handful of dust, pour goat milk over it, then we would circumambulate it.
Thus, the mission of our Master Prophet Muhammad (peace be upon him) brought about Islam, the last of all faiths, not only for Arabs but for all people. The Prophet (peace be upon him) was sent at a time when all people were in dire need of someone to bring them out of darkness into light.
This great Islamic faith is based on five basic principles, which are its pillars. They are mentioned in the Two Sahih (authentic) Books of Hadith (i.e. AlBukhari and Muslim) in the narration of Ibn `Umar (may Allah be pleased with them both) that the Prophet (peace be upon him) said, "Islam was based on five pillars: testimony that there is no God but Allah and that Muhammad is the Messenger of Allah; performing Salah (prayers), giving Zakah; fasting Ramadan; and performing Hajj (pilgrimage)."
The two Testimonies are the first and most important pillar of Islam.
The second pillar: performance of Salah (Prayer).
The third pillar: Giving Zakah (obligatory charity):
The fourth pillar: Observing Sawm (Fast) during Ramadan:
The fifth pillar is Hajj (pilgrimage to Makkah) to the Sacred House (Ka'bah).
Islam has other fundamentals that even if are not bases, they exist in the lives of Muslims and are applied to all matters. Among these principles is enjoining good and forbidding evil. Allah (Glorified be He) describes this Ummah (community sharing one belief) as the best Ummah