Understand with ease.

SURAH AL-IKHLAS (The Sincerity)

Bismillaahir Rahmaanir Raheem 

Qul huwal laahu ahad

Allah hus-samad

Lam yalid wa lam yoolad

Wa lam yakul-lahu kufuwan ahad

Say: He is Allah, the One and Only;

Allah, the Eternal, Absolute;

He begetteth not, nor is He begotten;

And there is none like unto Him.

The main theme of this Surah is Tawheed. 

To understand better, we need to understand the time period when this Surah was revealed.

It was back in Mecca, when the idolatrous polytheists were workshipping gods made of wood, stone, gold and silver with other substances. The gods had a form, shape and body. The god and goddess were descended from each other. No god/goddess were without a spouse. The stood in need of food and drink and their devotes arranged these for them. A large number of the polytheists believed that God assumed Human form and there were some people who descended from him. 

Although the Christians claimed to believe in One God yet their God also had a son, and beside the Father and Son, the Holy Spirit and also had the honour of being an associate in Godhead: so much so that God had a mother and a mother-in-law too.

The Jews also claimed to believe in One God but their God too was not without physical, material and other human qualities and characteristics. He went for a stroll, appeared in Human form, wrestled with a servant of his and was a father of a son, Ezra.

Beside these religious communities, the Zoroastrians were fire worshippers and the Sabeans Star worshippers.

Under such conditions, when the people were invited to believe in Allah, The One Who Has No Associate, it was inevitable that questions arouse in minds as to what kind of God it was, WHO was One and Only Lord?

It is a miracle of the Quran that in a few words, briefly it answered all the question present in the mind of people.

The Lord of the Universe is One.

HE has NO wife, NO children and NO son.

There is NO other god beside HIM.

Tawheed or oneness of Allah is the core of Islam. It is RIDICULOUS to suppose that the sun or moon is a god. In fact there is NO god but Allah ALONE with NO partner. 

Everything belongs to HIM and HE deserves All Praise, HE has power over everything.

Reference: Islamic Studies- Darussalam and Abul A'la Maududi, Tafhim al-Qur'an - The Meaning of the Qur'an