This short book about the Holy Spirit has been written to help young believers in Christ to understand what the Bible teaches about this important subject. We are informed from the Scriptures about who the Holy Spirit is and what He does. Like other books and booklets in this series, the style of writing has been kept simple. It will therefore be easier to read, and also to translate into other languages where this is necessary or helpful. The end of chapter summaries and optional study questions will help all readers absorb the subject matter and take their studies further.