Walk Score is a fascinating use of Google Maps to help you decide how walkable a given address or neighborhood is. There are ups and downs to living in a walkable area, so one shouldn’t interpret things as “positive” or “negative”. Just as one counter-example, a “green” rural home isn’t very walkable, but it’s certainly low-impact on the environment.
I live in Dallas, and got a walk score of 51. In reality, my neighborhood doesn’t lend itself very well to walking. We’re not too far from a large intersection with a grocery store and some restaurants, so that helps, but large blocks, dangerous walkways, and several mis-classified locations in Google Maps mean that the score has a bit of uncertainty in it. Still, the guide has some use and I think the score comes close to reality overall.