I may change the file name or move the file to another folder.
I would recommend you don't do that. Put the photo into its final destination folder straight out of the camera so you don't have to move it. If you must rename, rename within Lightroom.
If you have renamed and moved the photos outside of Lightroom, then you'd have to reconnect the photos to Lightroom one by one, using these instructions: http://www.computer-darkroom.com/lr2_find_folder/find-folder.htm
But really, change your workflow to eliminate as much of this unnecessary work as possible.
Your major problem is you don't understand how LR works.
LR is a Database that References, makes a record of, your images in the Database file, IE the Catalog file. You shouldn't be moving images around from outside of LR, like using the File Manager for your OS. 99% of all renaming and moving of images should be done inside LR. The 1% that shouldn't we won't go into here.
I suggest you view some of the excellent online tutorials for LR that are all over the net. Some even on Adobe TV.
I will look into that.
Thank you so so much!