Dhikr refers to the remembrance and worship of Allah through remembering His names and attributes. Du'aa refers to supplicating and praying to Allah alone for one's needs. The document discusses how Muslims are commanded to make dhikr and du'aa of Allah frequently, as a form of worshipping and remembering the Creator who has given humanity life and all possessions. It provides examples of common phrases for dhikr like "Subhan-Allah" and recommends following the teachings of the Prophet Muhammad on how to make effective du'aa.