I remember back when I was in college that in film... (
Julian, I think you may be a bit confused or misled about the roles of raw capture and Lightroom post-processing.
Raw capture is saving all the information from the digital sensor, with no processing. That's opposed to the camera processing the raw data into a JPEG, according to your menu choices.
With raw files, you always work on your computer with every last bit of what the camera recorded. With JPEGs, the bit depth has been truncated the moment after exposure to 8-bits-per-pixel (instead of 12 or 14). That severely limits the tonal range of the file. And the JPEG compression is lossy, so some data has been thrown away by compression, as well. You won't notice it right away, but each time you save a JPEG on top of itself, you throw away more data.
Where you see the difference is with very underexposed, overexposed, or poorly white-balanced images. Raw files can be stretched quite a bit to correct these errors, much like a negative could be in the film era. JPEGs are more like slide film.
Lightroom is the digital equivalent of a darkroom. It is a parametric editor, a database of image proxies and data, a print engine, an export tool, and a lot more. It is the central hub of a pro's software, ready to send files to Photoshop or various plug-ins and other applications. It's the central repository for finished image files, and the creator of multiple files for multiple uses of the same image.
Lightroom is designed to work with raw files, but it will edit TIFF, JPEG, PSD, and some other formats, too. Whatever you "store" in Lightroom isn't the original file, however. That remains intact. Lightroom displays a proxy image, and works on a copy of the original. To get an image out of Lightroom is to Export a copy, or Print, or send to Web, or make a Book... You get the idea. It is a "non-destructive" editor that leaves your originals alone.
Raw files from your camera are like latent images on undeveloped film. There's one important difference, though. You can edit and re-edit a raw file as many times as you like, and start every time with the original, unaltered data. That's like being able to develop the same film image in an infinite number of ways.