Alt text is what special-accessibility software uses to read the site aloud to a visitor with disabilities.
For each image, be sure to fill in the alt text field, which is in the Image tab in th editing ribbon.
For step-by-step instructions, please read:
To follow best practice for alt text:
Keep the alt text between 5 and 15 words.
Use keywords and other text that is meaningful to the website visitor, for example: if the image is about "cleaning a j-tube" use that text, not some other, formal language that the visitor won't understand.
Clearly and succinctly describe the image or link.
Do not include a file extension such as .jpg or .com.
Do not repeat the caption of an image, if there is one.
Don't include phrases such as "Image of . . .", "Link to . . .".
Every link should make sense if the link description is read by itself. Screen reader users may choose to read only the links on a web page. Certain phrases like "click here" and "more" must be avoided.
For more about alt text, see the website WebAIM (web accessibility in mind).
The description "two people" is poor alt text.
The alt text of "doctor talking to senior stroke patient" is better.