Lightroom is an Adobe product that is a powerhouse of an organizer, processor and output solution.
This a program that was designed with the professional photographer or serious amateur in mind. Like other editing software programs it gives you the ability to download and organize your files. In addition, you can further catalog your photos into collections, rate, label, flag and keyword tag them. If you are shooting a lot of images ,especially RAW format, this is the program that is really going to streamline your workflow. The following is a typical workflow scenario:
Let's say you go out and shoot a job, or just go out shooting for fun or even a vacation. You come home with a few hundred RAW files. After you download and sort out your images using Lightroom's flagging system you can select the 'picks' and the 'rejects'. You can then take the ‘picks’ and further rate them with Lightroom's rating system. So hopefully you have knocked down that file count to something more manageable.
You still have a hundred or so files that need to be 'developed'. Chances are you may have taken several photos in a row that may require similar adjustments. Lightroom allows you to make an adjustment to one file and then 'sync' those settings to any other files that would need that adjustment.
Next ,you have all of your files edited but they are still RAW files. Lightroom has a powerful export dialog box that will allow you to specify the criteria that a file needs to be exported as. For example, your client may want low res versions of those edited RAW files. You can create a low res preset and Lightroom will resize and apply all the export options to all the files you have selected including watermarking. You can then burn them onto a DVD, or email etc. Additionally the Print module in Lightroom has a lot of great templates and allows you to streamline your workflow there as well.
For all the power that Lightroom has it does not replace Photoshop. Although Lightroom has a couple of minor retouching tools in the Develop module it does not compare by any stretch to the retouching tools that Photoshop has. So if you are looking to remove or add things to photos or any other retouching work you will have to take the file from Lightroom and continue to edit it in Photoshop. The good news is, after you are done editing the file in Photoshop when you save it, it goes right back into Lightroom.
Generally speaking if Lightroom becomes part of your workflow solution you will probably spend about 85% of your time working there. The other 15% will be spent either using plug-in programs or editing in some version of Photoshop.