The Christian bible tells us God is the alpha and the omega, the begging and the end; and there are none like him. The law of conservation of energy tells us that energy cannot be created or destroyed, while Albert Einstein tells us that energy and matter are interchangeable with his equation E=MC^2. This makes understanding what God is very simple, God is pure energy. In this sense of God, I include God the Father, God the Son, and God the Holy Spirit.
This definition allows God to be omnipresent, all powerful, and a trinity in one body without violating what the Christian bible says or breaking any laws of physics. In accordance with Christian scripture this infinite state of pure energy which is God is also known as Everlasting. From Everlasting-to-Everlasting God will always exist for there are none other like him.
Psalm 90:1-2
1 Lord, thou hast been our dwelling place in all generations.
2 Before the mountains were brought forth, or ever thou hadst
formed the earth and the world, even from everlasting to everlasting, thou art God.
Psalm 86:8-10
8 Among the gods there is none like unto thee, O Lord;
neither are there any works like unto thy works.
9 All nations whom thou hast made shall come and
worship before thee, O Lord; and shall glorify thy name.
10 For thou art great, and doest wonderous things: thou art God alone.
Revelation 22:13
13 I am Alpha and Omega, the beginning and the end, the first and the last.