God is a Trinity, but so are humans. For God, the Trinity is the Father, the Son, and the Holy Spirit. For humans, the trinity is the soul, the body, and the spirit.
The Soul. Like the Father, the human soul is non-physical and eternal. The soul consists of personality, will, emotions, and the mind. The soul is the seat of a human's authority and free will. Critical thinking, decision-making, values, beliefs—all of these reside, take place, or emanate from within the soul.
The Body. Like the Son, the human body exists within the physical realm. We use our human bodies to interact with others, to create, to communicate. The human body Christ took on at His birth in Bethlehem was just like ours—subject to corruption, meaning it would perish someday. But because Christ is God the Son, He has the power to overcome death. After His death on the cross and burial, He defeated death and took on an imperishable, resurrected body. Christ-followers will also receive an imperishable body someday.
The Spirit. Like the Holy Spirit, the human spirit is non-physical. But unlike the Holy Spirit our spirits are dead when we are born—because of the sin nature humans inherited from Adam. Think of our dead spirits this way: we're like an automobile with a dead car battery. Because we don't have any power of our own, we're unable to fulfill the purpose for which we were designed. Our spirits must be brought back to life by the Holy Spirit, like a car battery getting charged up.
Genesis 1:26-27 says God made us in His image. And if you think about it, humans are a trinity just like God.