The home screen shows a list of individual carwashes (or other participating sites), listed in order of distance from your current location. Alongside each one you will see your washbucks balance for that vendor. Because the Tap & Pa$$ app can be used at different vendors, you will have a separate Washbucks balance for each vendor you have made a purchase at, so you will see different amounts for carwashes owned by different companies.
Each location that you have a Washbucks balance for will display a bar graph - this shows you how far away you are from being able to buy a carwash or other product with your Washbucks balance. The product shown is just an example - you can use your Washbucks to pay for any product available at the location, and can also pay partially with Washbucks and partially with cash.