Look to the right hand side of this page, under "More like this" you will see a previous question called "Can I simply move my main pictures...". This details the procedure for re-assigning pictures to Lr.
In future, move your pictures from within Lr, and not using Windows Explorer ( if you're using Windows), so that it does not lose track of them.
Apparently the title of your post is misleading and it was not the catalog that you moved but rather the photo files - which makes me think that you do not understand the structure and method of operation of Lightroom. (You are far from alone in this.) The catalog is a single file with the extension *.lrcat and it exists entirely separately from the photo and video files and can be anywhere, on any local drive, but not on a networked (remote) drive/server. It is simply an index of your photos and moving it doesn't affect the photos themselves or change their locations and cause the "?" and "!", any more than moving a phone book which lists your name and address would cause you to disappear. But if you leave town, somebody trying to find you using the phone book will not succeed. If you moved the photos, you now have to revise the catalog and bring it up to date, as explained in the link to which John sent you.