For example, a photo of Pure and Precious Vitamin C Serum could be called ‘Pure and Precious Oils Vitamin C Serum or could have a longer description with some keywords up to about 100 characters.
They will also be visible when you hover your mouse over an image that is unable to load, plus helps people who use screen readers and other assistive technologies. A good description would include information about product use:
Pure and Precious Oils Vitamin C Serum helps fade Sunspots, Age Spots and Acne Scars (84 Characters)
You can always change the Image Description and Alt text within the Media Gallery later if you forget. Sometimes it is easier to do so. I hope this tip helps!