
Use "alt text" to provide an alternative way for a screen-reader user to know what an image depicts.

The rationale for using an image is important for determining what the alt text should be.

Specific use: If you are using the image for a distinct purpose, the alt text should describe the image well. For example, if you were using the photo above for a botany class, you might write alt text that reads "Hydrangeas, which thrive best with full sun in the morning."
Decorative use: If you are using the image for illustration, the alt text can be simple. For instance, with the photo above, you could enter "Flowers." Some platforms will provide a checkbox for you to note that the image is merely decorative, thus requiring no alt text.