You can move your catalog to a different location on your computer's hard drive, to an external disk, or to another computer altogether. Simply use the Explorer (Windows) or Finder (Mac OS) to drag or copy the following files to the new location:
To transfer a catalog between a Windows computer and a Mac, copy your catalog, preview, and image files from the original computer onto a flash or other external drive. Then, attach that drive to the second computer and copy the files to the desired location on the second computer.
For a video on how to move a catalog between two computers, watch Julieanne Kost's How to migrate Lightroom to another computer on Adobe TV.