Article 8: The information provided about the purpose of travel and the conditions of stay in Schengen countries is not credible. What does this mean?

The itinerary is only one aspect, and as long as it is reasonable, it will not go in this direction.

You can check whether you have provided the hotel confirmation form and air ticket to determine the travel itinerary. If you choose the train as the means of transportation between European cities, you'd better provide the reservation of train tickets.

One more thing to know: if you travel alone (especially if you have family), you will be more likely to be refused a tourist visa.