Final answer:
Water-based lubricating jelly is used to reduce friction between body surfaces or medical instruments during medical procedures and sexual activity.
Step-by-step explanation:
Water-based lubricating jelly is used for a variety of purposes in healthcare settings and for personal use. One of the main reasons is to reduce friction between body surfaces or medical instruments, allowing for smoother movement. For example, it can be used during medical procedures like ultrasonic imaging to lubricate the skin and reduce friction between the transducer and the skin, making it easier to move the transducer over the skin. Water-based lubricating jelly is also commonly used during sexual activity to provide lubrication and enhance comfort.