Lightroom is just an image manager (that requires adding everything to a catalog), ACR interface, and metadata editor for digital photography.
Photoshop is a high end image editor that supports large images; many file formats; many image modes and depths; many compositing, filtering and image adjustment operations, etc.
Photoshop can do what Lightroom can do other than the catalog management, but Lightroom does a small fraction of what Photoshop does.
Tom O\'Connell wrote:
Is there a list of what photoshop does that lightroom doesn't?…
That "list" would turn into a book—or at least a substantial booklet.
Some of us who have been using Photoshop for over a decade feel no need for Lightroom. It's very useful, however, for professional photographers who have to deal with thousands and thousands of shots. It's all about volume.
Far from being a pro photographer, I tested Lightroom when it first came out and absolutely hated it. But that's just me,
Goodness. That's as good a short comparision of the two apps as I have ever seen. I wonder if there is friendly rivalry between the teams?