A viral vector is a tool used in gene therapy to deliver genetic material into cells. It is derived from viruses that have been modified to be safe and non-infectious. By using these vectors, scientists can introduce new genes into a patient's cells to treat or prevent diseases, such as certain types of cancer or genetic disorders. These vectors can carry specific genes that help the body produce proteins it may be missing or malfunctioning. Common types of viral vectors include adenoviruses, lentiviruses, and adeno-associated viruses. Their ability to efficiently transfer genetic material makes them valuable in research and medical applications.