Omniscient is one of those fancy, theological words that people seldom use and many do not understand. If it is so difficult to understand, then why even bother to bring it up? My reason - to challenge you to consider the attributes of God. For, to know God is our highest calling, our chief goal in life.
A.W. Tozer, in his book, The Knowledge of the Holy, gives meaning to the word omniscient, "To say that God is omniscient is to say that he possesses perfect knowledge and therefore, has no need to learn. But it is more; it is to say that God has never learned and cannot learn."
We can add, that nothing escapes his attention. He is mindful of everything; everything concerning me, everything concerning his kingdom, and yes, everything concerning the world. He knows all things. Nothing is hidden from his watchful eye. My mind is limited. I only know what I see, what I hear, or what I experience. God can see in the darkness; he knows the private thoughts of every person. He is not limited by time, as we are, but sees the past and the future as well as the present. His word tells us that he knows the number of hairs on my head. For that matter, he knows my heart rate, my blood pressure, my cholesterol count, you name it, he knows it. God has intimate knowledge of me. He knows what I will do even before I know I have a choice.
Oh the depth of the riches both of the wisdom and knowledge of God! How unsearchable are his judgements, and his ways past finding out! Romans 11:33