The five pillars of Islam
Islam has been built on five pillars. These are the five most important and distinctive acts of worship. Prophet Muhammad said:
Islam has been built on five [pillars]: testifying that there is no god but Allah and that Muhammad is the Messenger of Allah, performing the prayers, paying the Zakat, making the pilgrimage to the House, and fasting in Ramadan.
The declaration of faith
"I bear witness that there is no deity worthy of worship but Allah, and I bear witness that Muhammad is the Messenger of Allah.". The first part of this simple sentence shows in a clear and concise way the foundation of Islam: pure monotheism. The second part is the acceptance of Muhammad as a messenger of Allah and includes accepting the message that Allah revealed to him: the Quran and his Sunnah (prophetic way). Whoever states this declaration of faith, believing in it and acting upon it, is a Muslim.
Know that there is no deity worthy of worship except Allah
Prayer
Allah has prescribed five mandatory daily prayers. They must be performed while in a state of ritual purity, and they consist of reciting the Quran, bowings and prostrations.
Indeed, those who believe and do righteous deeds and establish prayer and give zakat will have their reward with their Lord, and there will be no fear concerning them, nor will they grieve.
Zakat
Charity is a noble act and Islam promotes it. Islam encourages Muslims to give to charity often and to help those in need. Zakat is a specific type of charity that those that are wealthy give yearly to those in need.
And establish prayer and give zakat and loan Allah a goodly loan. And whatever good you put forward for yourselves - you will find it with Allah. It is better and greater in reward.
Fasting
Allah has commanded us to fast during the month of Ramadan. Fasting starts when the daylight can be distinguished in the horizon and ends when the sun sets. While fasting, Muslims must refrain from eating, drinking and having intimacy.
O you who have believed, decreed upon you is fasting as it was decreed upon those before you that you may become righteous.
Pilgrimage
Muslims are required to make pilgrimage to the House of Allah, the Kabah, at least once in their lifetime, if their economical and health circumstances allow them. The Kabah was built by Abraham and his son Ishmael, and it has been a place of pilgrimage since it was built.
In it are clear signs [such as] the standing place of Abraham. And whoever enters it shall be safe. And [due] to Allah from the people is a pilgrimage to the House - for whoever is able to find thereto a way.
