When adding images to a web page, it is important that they have "Alternative text" and "Captions". These are used to describe images and will ensure they are accessible to everyone and could improve the search ranking.

Alternative Text 

Alternative Text or Alt text is a text replacement for an image and is used to explain what the image is and what the image is trying to convey to the user.

Captions for images?

• Captions are text descriptions of an image that are displayed under the image.
• They can explain the context of the image.
• Captions can be used to credit the source or copyright.