Why is gearbox used?

Why is a gearbox utilized in various applications, and what are the key benefits it provides? How does it enable the transmission of power from one source to another efficiently, allowing for varied speed and torque outputs? Is there a specific industry or machinery where the use of a gearbox is particularly crucial, and why is it so important in those cases? Additionally, are there any modern advancements or innovations in gearbox technology that have further enhanced its performance and capabilities?