Islam is like a building and it has five pillars. As a building can not stand without its pillars the building of Islam also can not stand without these five pillars. These five pillars are the base of Islam.
The first Pillar of Islam is witness of Toheed O Risalat. The second one is to offer prayers five time a day. Third is Fasting for the whole month of Ramadan. The fourth pillar is Zakat. The fifth and the last pillar is Hajj.