When creating a Google Slides presentation, it is always a good idea (and sometimes legally required) to make it as accessible as possible. There are several ways to do this, including:
- using tables
- working with high contrast colors
- using informative link text
- using numbered and bulleted lists
- incorporating slide numbers
- and using automatic captions.
For more information about these things, visit Google's "Make your document or presentation more accessible" page.
Alternative text is used by a screen reader to describe an image to a user who may have a visual impariment. Without alternative text, a screen reader would simply read, "image" when encountering a graphic. Alternative text will help users know what the image is and how it fits in the text and should be added for images, photos, drawings, and other types of images.