This app measures the distance you walk in a given amount of time. This is sometimes called "Timed walk test". The distance you walk in the chosen time can be used as an indication of your exercise capacity and general health status.
The app measures the distance you walk using the positioning systems embedded in your phone, like the GPS. You therefore need to use it outdoor or it may be not possible to measure the distance.
Even though the algorithm that estimates the walked distance has been validated in clinical settings (see https://mhealth.jmir.org/2020/1/e13756/), this app is not a medical device. It should be used for general well-being or as a home-based complement to conventional clinical assessment.