Shooting in RAW vs JPEG
This is a question, not just for those new to photography, but also existing professional photographers. I know of several professional photographers who shoot JPEG files, as opposed to RAW images, for varying reasons.
Switching to the RAW file format means you choose how to make the adjustments to the image - as opposed to the camera trying to do the editing on your behalf. Of course, if you choose the RAW file format, you will have to complete the editing of your photograph in Lightroom, or another piece of editing software. The JPEG format will possibly mean less editing on your computer (partly because the camera may have done a good enough job already - although for professional use, editing will almost certainly take place on every image).
When it comes to editing in Lightroom, a RAW file can be manipulated much easier without witnessing the image degrade (shown as 'digital noise') - mainly due to the camera storing all of the information from the original exposure - as opposed to a JPEG file, which discards any information it feels is unnecessary.
As JPEG files do discard some information that is felt unnecessary, the actual files will be smaller than an equivalent RAW file. This can be important for some people worried about storage costs.
So, for total control of our images, choose RAW - but be prepared to do more editing in Lightroom (and you may find Lightroom operates slower when editing RAW files). Choose JPEG format if you either don't want to do any further editing, or are very happy with the cameras best guess at editing for you.