"Zoom functionality" refers to the ability to make things on a screen appear larger or smaller. It allows you to zoom in to see details more clearly or zoom out to see a wider view. Full definition
While I'm a huge fan of the pinch to zoom functionality in the web browser, I think a little additional height would make the display that much better for a touchscreen. (crackberry.com)
Beyond that, the camera features optical image stabilization, electronic image stabilization, and a more mechanical zoom functionality. (androidheadlines.com)
The S9 Plus will feature a dual camera with ability to offer optical zoom functionality, while the S9 [the smaller of the two phones] will only boast of a single module. (socialbarrel.com)