I think of an alley as the route less traveled through my neighborhood. They often extend for many blocks. Alleys are great for foot and slow bike explorations because people seldom drive in them except to park their cars.
Some alleys are paved, some are not.
Alleys are a great place to store garbage cans, recycling bins and yard waste containers,
You might even find a Honey Bucket in an alley!
The alley side of a home is popular with gardeners. It's possible to spot greenhouses, vegetable patches, raised herb beds, and flower gardens on an alley exploration. You might get lucky and spot the gardener in action as well.