What is the purpose of the `alt` attribute in HTML?

The alt attribute in HTML serves an important role in enhancing accessibility for web content. It is used to provide descriptive text for images, which is especially beneficial for users who are visually impaired and utilize screen readers. When the screen reader encounters an image, it reads the text present in the alt attribute, allowing users to understand the content and context of the image even if they cannot see it. This descriptive text also appears in place of the image if the image fails to load, ensuring that the information is still conveyed to all users.

The inclusion of the alt attribute contributes to making web pages more inclusive by accommodating a wider audience and ensuring meaningful interactions with content. While other options mention functionalities like tooltips, alignment, or specifying sources, none provide the significant accessibility benefits that the alt attribute offers.