There are five pillars
that hold up the structure of Islam

One of the main differences between Muslims and non-Muslims is that we
Muslims declare what we call the Shahada,
or, Declaration of Faith.

The Shahada is the first pillar of Islam

The Shahada goes as follows:

"La Ilaaha Ill Allah, Muhammadun Rasul Allah"
(There is no God but Allah, Muhammad is the Messenger of Allah)

The second pillar of Islam is Salah (Prayer)

We don't only pray Salah because we're told to,
We pray Salah because it helps us remember Him (Allah),
and makes us get closer to Him.

In the Holy Qur'an it is said:

"Establish Salah to remember Me (Allah)." (20:14)

We pray Salah five times a day.
The five Prayers are: Fajr, Dhur, 'Asr, Maghrib, and 'Isha

The third pillar of Islam is Zakah (purifying or cleansing)

Zakah is an annual mandatory payment of 2.5% of the Muslim's savings.
This act of Ibaadah (worshipping) is meant to keep our wealth clean from greed and selfishness.

In the Holy Qur'an it is said:

"Alms are for the poor and the needy, and those employed to administer the (funds);
For those whose hearts have been (recently) reconciled (to truth);
For those in bondage and in dept; In the cause of God; and for the wayfarer;
(Thus is it) ordained by God, And God is full of knowledge and wisdom." (9:20)

With Zakah, we enjoy an opportuniy of sharing our wealth with the less fortunate.

Sawm (fasting) is the fourth pillar of Islam

Fasting is another act of Ibaadah.
In Ramadan, the 9th month of the Islamic Calendar,
fasting is made mandatory for all adults.
While fasting, we Muslims must abstain from eating, drinking,
and having conjugal relations from sunrise to sunset.

In the Holy Qur'an it is said:

"O you who believe; Fasting is prescribed for you
as it was prescribed for those before you
so that you may learn self-restraint." (2:183)

Fasting makes us feel hungry and therefore helps develop our feelings for the poor.
Fasting helps us to learn self-control, and helps us overcome bad habits
such as selfishness, greed, and laziness.
(Isn't that cool?!?)

The final pillar of Islam is Hajj (the Pilgrimage to Makkah)

During this Pilgrimage, we go to visit the Ka'bah, the house of Allah.
This, too, is manditory, as all the other pillars of Islam are.
But the only difference is that Hajj is only compulsory
for those that can afford it.

In the Holy Qur'an it is said:

"And complete the Hajj or Umrah in the Service of Allah..." (2:196)
Umrah is like a mini-Hajj.

Well, I guess that's about it.
Those are the five pillars of Islam,
Shahada, Salah, Zakah, Sawm, and Hajj.