Describe is a feature that automatically generates a prompt based on an uploaded image. Just upload your image and click the "Describe" button found under the image input field.
The Describe feature
Keep in mind any text in the Prompt field will be overriden by the output of Describe. While Describe aims to create a prompt for similar-looking images, it may not always be perfect. For best results, consider using it with 1.5 based models.