Many people, including myself, have used one catalog to manage thousands of images. This may not be the best strategy, depending ob what your needs are.
Regardless, you may find yourself wanting to create a new catalog with existing photos from say, an existing folder in your present catalog. Creating a new catalog and then importing that folder into it isn’t a good idea if you want to retain all of your edits.
This video will show you the correct way to do the above in order to retain all of your editing info: