Please explain what the trinity is? If God is one, why is He divided into three?
Understanding the Trinity is a difficult subject. It is difficult because no one understands God. We cannot touch Him. We cannot see Him (John 1:17). We cannot examine Him. So what is He like? If we do not understand something, it does not mean it is not true. It has been said that if we could understand everything about God, He would not be God.
We know that God is spirit (John 4:24). The Bible teaches us that He knows all things, is all powerful, has always existed and sees everything. The Bible tells us that Jesus walked through walls (John 20:19-20). He just vanished while talking to His disciples and then reappeared (John 24:31-36). What kind of being is God? Probably the best passage in the Bible to explain our situation is,
Can you discover the depths of God? Can you discover the limits of the Almighty? Job 11:7 (NASB)
Behold, God is exalted, and we do not know Him; The number of His years is unsearchable. Job 36:26 (NASB)
The Bible teaches there is only one God. Yet, we read that the Father is God, Jesus is God, and the Holy Spirit is God. We try to capture this concept of God who is a plural-one with the term “trinity.” The Bible never uses the term trinity. But it is clear there is only one God (Isa 44:8; 46:9). And it is clear the Bible teaches that Jesus Christ is God, the Holy Spirit is God and the Father is God. If we do not understand something, it does not mean it is not true.
The Bible teaches that God is a plural-one. God is a mystery. We must believe Him in what He says about Himself.
Reference Links:Sin and Salvation
Who Is God?
The Trinity Mystery, part 1
The Trinity Mystery, part 2
Is the Trinity equal even though they have different roles?