The pillars of Islam are…
1. The belief (Imaan): That there is no God to be worshipped except Allaah (the one God) and that Muhammad (peace and blessings of God be upon him) is His Messenger.
2. Performing the prescribed prayers (Salaat): five times a day.
3. Fasting (Siyaam): Once a year, from sunrise to sunset throughout the entire month of Ramadhan.
4. Charity (Zakaat): Which is paid to the poor and needy once every year.
5. Hajj: Which is the pilgrimage to Makkah once in a lifetime if one is physically able and can afford it financially.
Pillars are part of a building. The building in this case is the perfect human being who cares and protects the rights of all creations and fellow humans, thus establishing a society in which truth and justice and peace is supreme.
Reference: www.islamway.com