Lower Quality

Hi!

I am an amateur photographer/editor, so im not too advanced with this stuff. When I am looking at a photo on my camera screen, and I zoom in the quality looks just fine, but once the same photo is in lightroom zoomed in the exact same way it was zoomed in on my camera, the quality is much much lower, to the point where the photo is unuseable. Like I said, I am an amateur so im not sure why this is happening and if there is a fix. For my camera, all my shots are shot in "Fine"

Thanks