Omnipotence means all-powerful. Monotheistic theologians regard God as having supreme power. This means God can do what he wants. It means he is not subject to physical limitations like man is. Being omnipotent, God has power over wind, water, gravity, physics, etc. God's power is infinite, or limitless.
Omniscience means all-knowing. God is all all-knowing in the sense that he is aware of the past, present, and future. Nothing takes him by surprise. His knowledge is total. He knows all that there is to know and all that can be known.
Omnipresence means all-present. This term means that God is capable of being everywhere at the same time. It means his divine presence encompasses the whole of the universe. There is no location where he does not inhabit. This should not be confused with pantheism, which suggests that God is synonymous with the universe itself; instead, omnipresence indicates that God is distinct from the universe, but inhabits the entirety of it. He is everywhere at once.