Add Alternative text to your images to allow screen readers to read them. The text should be brief and descriptive, a stand-in for the image itself.
Best practice: Use "President Barack Obama greets Hillary Clinton" rather than "Image of President Barack Obama greeting Hillary Clinton"
Best practice: If an image conveys textual information such as "New!" or "Tip!" simply use that text as your Alt text.
Best practice: If the image is linked, use the same text you would use if it were a text link.
Best practice: For infographics, you will need to use something besides Alt text to help blind users. Alt text has a 125-character limit, so you should offer the infographic content in a structured list or other organized content structure as an alternative.