Even if you and your family attend church and have knowledge of the Bible, God can seem like a remote concept instead of an entity that is the embodiment of love. Help your child understand with simple explanations that focus on specific aspects of God and how they apply to his life. That will help your teen to relate to God on a personal level.
Teach your teen about the personhood of God. Your child is old enough to understand that God is referred to as "He" because we relate to Him as a person, although we have never seen Him. Explain that God is a spirit that is present in the invisible realm. He can see and hear everything that occurs. He is also eternal. This might be intimidating for your teen so remind him that God's spirit is a source of comfort and help even when we don't realize it.
Explain the character of God. Tell him that God is good, loving, forgiving and merciful. Then tell him that God is also a God of judgment, discipline and wrath. Correlate this to the court system. Judges often have mercy on offenders and will sentence them to lighter punishments, but they have to demand accountability. Emphasize that God is the ultimate judge who always dispenses justice correctly.
Teach your child about the actions of God. Explain that God created the world and everything living in it -- human, animal and plant. He is sovereign over the events of the world and controls the weather, including the sunrise and sunset. This might give assurance to your child that someone is in control even when chaotic and unexplained events occur.
Explain God's omniscience and omnipresence to your teen. It might be a bit difficult for teens to understand that somebody can be all-knowing and all-present. To make this clearer, ask your teen to think of God as a parent. Although you would like to know everything about him and be with him everywhere, you are limited by time and space. Explain that God is under no such restrictions.
Use biblical passages to reinforce your explanations. The first three chapter of Genesis give an account of creation. Many of the Psalms tell of God's goodness and the New Testament book of 1st John emphasizes His love. These scriptures might give your child a deeper understanding of God.