You import the raw files from cameras that are supported by Lightroom.
Yes, those are good links, but let's clean up the terminology too so we're all talking the same language.
There is no "open" in Lightroom when referring to photos.
You can "import" photos into Lightroom ... this means that now Lightroom has registered the photo's location and other pertinent information into its database, but it does not store the photo itself in the Lightroom database (or anywhere else in Lightroom), so Lightroom never contains your photos; the photo continues to be stored on one of your hard drives, wherever you want it to be, and the file is visible in your operating system.
Once you have imported the photos, then Lightroom can perform tasks on the photos, such as Develop, Print, e-mail or upload, etc. and once you have imported photos into Lightroom, you should not move or rename or delete them outside of Lightroom.