I've imported some raw images from camera and made changes. When I close and reopen LR I can still see the changes, but my original important RAW file is intact. So I'm curious, where/how LR keeps my changes on top of RAW file? Can I make my changes on imported RAW file? Say want to crop imported file and keep just cropped version.
Lightroom does not make changes to the original file. It stores the actions of each edit in the LR catalog. When you Export an image to, say a JPEG, LR performs each of those actions, creating a new file, in this case a JPEG. It never alters the original. The RAW file isnt really an image, but data that was recorded by the sensor. You see an image in preview because the RAW file actually stores a small JPEG preview image within the file. So 'cropping' the RAW isn't meaningful. You instead use the RAW data to create an image that you can crop as your final output. The output can be JPEG, TIFF, PSD, DNG, etc.
The catalog location can be found by looking under Catalog Settings.
You can also ask Lightroom to store these same edit actions in a 'sidecar' file, which will be stored alongside (in the same directory) of your RAW image, by selecting "Automatically write changes to XMP" in the Metadata tab of Catalog settings.