Zoom (also called magnification) makes everything on a screen bigger. It is a recognised accessibility feature for a website because it helps users who need larger content to read and view it.
When you explain zoom as an accessibility feature, you must say that it enlarges both text and images. Simply stating that the content becomes easier to see is not enough. For example, on a school cooking club website, you press Ctrl and + to zoom in. The recipe instructions grow larger, and so does the photo of the finished cake. Both parts of the page are magnified.
Increasing or changing the font size is not an accessibility feature for a website, because the browser already lets each user choose their own text size, so the website itself is not providing the accessibility. For a website, use zoom or magnification instead.
On a device or in an operating system, adjustable typeface and font size are accessibility features. For example, a games console's settings let a player switch to a bold typeface and make the menu text larger. Modifications for visual needs include making sure text on screen can be made large enough to read comfortably.
Pearson BTEC Digital Information Technology · Accessibility