Though the process is different, the end goal is the same- MOISTURE IN YOUR HAIR
Hello Belle,
Let’s jump right into the difference between Hair Hydration And Hair Moisturizing.
Hair Hydration is the process of getting your hair strands to absorb water- this happens usually when you have your ‘hair wash-day’ or you run a bath from your hair strands down.
After this process, it is expected that the moisture in the hair strands will eventually dry out hence, the need to lock up the moisture gotten during the hair hydration process which is where Hair MOISTURIZING comes in.

Hair Moisturizing is the process of locking water or moisture in the hair strands. This can be done with any product, process, or tool like the hair spray bottle to slow down water from evaporating from your hair.
Simply put, hydration involves absorption of moisture into the hair whilst hair moisturizing is the retention of the moisture in the hair to enhance healthy hair.