Gary: If someone gives me a photo to look at on a memory stick or card, is there a way to view the photo in Lightroom Classic without having to import it?
Andrew: Yes, you can preview the photos in Lightroom Classic’s Import window.
The default viewing mode is Grid View, which looks like this:

You can move the Thumbnails slider to adjust the size of the previews.

You can also switch to Loupe View by clicking the icon under the thumbnails or with the ‘E’ keyboard shortcut.

This gives you a clearer view of your photos. Use the arrow keys on the keyboard to move through the photos, and the Zoom slider to zoom in.

One use of Loupe View is to decide which, if any, photos to exclude from the import. Uncheck the Include in Import box under the photo to remove it from the import.