Street View on Google Maps is a tool developed by Google to be used in conjunction with Google Maps. With it, you can see a photographic representation of the area where you are.
All you need to do is activate the application and you'll have a photo of the area you have selected on your smartphone. The app is especially useful to find places within an area where you'd like to go, but are unfamiliar with.
Street View on Google Maps usually comes installed on all Android devices, but it is better to check and make sure you have it on your phone. You never know when you'll need it.