Lightroom is good for sorting through your library and editing several images at a time. You can easily rate, view metadata, filter, and copy settings from one photo to another. However, after a certain point it becomes limited with how you can edit an image. For example you can't combine multiple images like in the post above.

Which is where Photoshop comes into play. Photoshop allows for very advanced editing but you can pretty much only edit one image at a time. There are ways to multitask but it's not as intuitive as Lightroom.