The Zoom tool lets you zoom in close to certain areas of an image, and zoom out to get more of a bird's eye view of what's happening.
In the top menu bar, choose View > Zoom In or View > Zoom Out.
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To use the Zoom Tool
Either select the zoom options from the "View" menu (as shown above). To use the keyboard shortcut, hold ALT (PC) or Command (Mac) and press + to zoom in, and ALT (PC) or Command (Mac) and press - to zoom out.