The alt text is a HTML tag associated with pictures and graphics within your HTML of your web page. People that are considered visually impaired may utilize a screen reader. The screen reader will actually read the text and the images on the website. So, if you have an image of a butterfly, you will want to fill in the alt text field describing the butterfly. Most photos that are taken by you may be automatically labeled “11100033.jpg.” I will even change the name of the photo once I optimize the size in Photoshop to “monarch.jpg.”
<img src=”11100033.jpg” alt=”monarch butterfly on green grass” />
Within the HTML code, the alt text will appear as:
<img src=”11100033.jpg” alt=”monarch butterfly on green grass”>
Most content management systems (CMS) will have a field to populate your alt text. Within WordPress, you will find your alt text field when you upload your photo and publish to your web page. One thing to note, never “pad” your alt text with a bunch of garbage keywords. Google will flag this as spam and you may actually lose position.
This is a very basic synopsis on the importance of alt tags. For more information, please see Google’s article on alt tags here: Google Alt Tags