Do you have a catalog already? If you imported images into Lightroom, then the catalog and the photos are in the cloud. If you imported images into Lightroom Classic, then the photos and the catalog are on your computer.
In both cases the application is separate from the catalog, so if you delete the app you won't lose your catalog, but you will lose the ability to view the catalog.
LR classic is the version with your catalog. It is the son of the original Lightroom. The other version is the cloud version For unknown reasons, Adobe have picked up the option to get all their users confused in naming the new program with the same name. Destroy the cloud version.