Overall meaning :
Allah Almighty proclaims that all praise belongs to Him alone, who created the heavens and the earth and made darkness and light. Yet, despite all this, the unbelievers set up equals to their Lord and worship them besides Him.
He then states that it is He who created all human beings in the very beginning from clay—by creating from it their father Adam, from whom they have all sprung—then He decreed a fixed term for their stay in the worldly life and a fixed term for the period of the worldly life, known only to Him, after which they will all be resurrected so He will repay them according to their deeds. Yet, despite such perfect clarification and manifest evidence—having learnt that they were created from clay and that their life terms will expire—they still doubt the resurrection and final judgement.
After that, He declares that He is the only God deserving of worship in the heavens and the earth, who knows all that people keep secret as well as all that they do openly, and is fully aware of all their good and evil actions, of which He keeps count and will repay them according to them.