The app keeps a record of your rides. It is interested in time and distance and the conditions of the ride. It is not interested in your performance, but you can get your rides from Strava or from spreadsheets.
You can put parts on your bikes and keep track of how they are used. This can help you or your bike mechanic spot where parts are wearing and likely to be in need of servicing.
By answering a few simple questions, the app can help point you in the right direction to sorting out that irritating noise or why your gears don't work.