If the original is missing, then I don't think so. Trying to go to the Develop module will likely show "The file could not be found." and the tools will be disabled. If you have Smart Previews available, it might let you make changes with the smart preview, but you won't be able to export without access to the original image.
If the images are available somewhere else (like on an external drive or something), you can update the location of the folder to point to where the files are.
does this mean I have lost the images even though I can still see them in my LightRoom folders?
It depends. But if you are in Lightroom and can "see" your images, you could just be seeing the preview files that were generated when Lightroom had access to your original files. If you see a question mark on top of the image or the folder, that means that Lightroom doesn't know where the original images are. Under the image preview on the top right, it may also say "Original file missing".
If you moved the folder outside of Lightroom, then Lightroom just doesn't know where you moved them to. You can right click the folder and locate it on your hard drive. But Lightroom does not store the original images inside of it's catalog, just pointers to your images.
Why are the image is no longer on your PC? Did you delete them? Preview images are generated by Lightroom, but they are not something that can be edited. You need your images. What happened to them?