First, while Lightroom has not yet received the enormous publicity that Photoshop has (Lightroom, for example, has not yet become a verb. No one says “Lightroom it!” yet) Lightroom is incredibly powerful with amazing capabilities.
Second, consider Lightroom as a digital gateway drug. Photoshop might come later, once you’re hooked. You may actually become quite enamored with Lightroom however, and decide to completely forego Photoshop altogether. Many do. You may even decide make Lightroom a verb.
So? Get to the point.
Here’s my point (or at least one of them): Lightroom is much easier to learn with far fewer tools to master than Photoshop and it has some nifty features that Photoshop doesn’t. Quit Lightroom while working on a photo (you don’t even have to save it!) and when you return, Lightroom remembers every change you made in its History panel. Quit Photoshop and its History panel will be empty when you return to work on the photo! Plus, you may have heard those techie folks tossing around the word “non-destructive” editing*. That is totally true for Lightroom, but not always true for Photoshop.

Every change you make is recorded in the History Panel making your changes “non-destructive”
*Non-destructive means the original photo is not actually being modified. Instead there is a list of instructions that tells Lightroom what you did. Those instructions can be deleted or reset at any time, which will leave the original photo untouched.
Please, read on. I’m almost done.
Before digital, amateur and professional photographers alike made prints using some basic tools for dodging and burning in the darkroom. They rarely purchased a compliment of special films, exotic tools and devices to make multi-element photo-composites from their photographs. (Yes, I know there were a few photographers who did that, but we’re talking about rest of us.) That’s the elemental difference between Lightroom and Photoshop: Photoshop is like an exotic high maintenance, manual stick shift luxury car with a basic stereo radio and CD player; whereas Lightroom is a completely assembled, ready to use high-end, Dolby 5.1 sound system with six-foot speakers*. Let’s face it. Many of us would take the car but wouldn’t know how to drive it. However, if you just wanted the music and didn’t need the ride, which would you rather listen to?
Okay now, the choice is yours. If you want to do hard-core, multi-element photo-composites, Photoshop is definitely the place to be. But in my opinion, if your goal is to organize, keyword and develop your snapshots into full-fledged photographs, Lightroom is the program you’re looking for.
* Please note that Lightroom® does not come with a sound system, nor does Photoshop® come with a luxury car. I was just using metaphors.