Sawm literally means ‘abstinence’ - and in the Islamic sense - Sawm is to abstain from food, drink and marital sex - from dawn till sunset - in the Islamic month of Ramadan. The ultimate reason Muslims fast in the month of Ramadan, is to attain Taqwa. And Taqwa, is to become aware of your conscience
Zakat is both charity and tax. Zakat is considered charity - when paid voluntarily, without specifying an amount. But Zakat is also a tax - if a specific amount is a requested by the State. Zakat was initially a voluntary contribution, that eventually became an obligatory duty.
The Shahadah is the first pillar of Islam and is ones declaration, intention and proclamation to join or be a part of the Islamic faith. The Shahadah serves both a religious and political purpose.