On the European Youth Portal, you can find practical information and useful tips about travelling in Europe. 

You must possess a valid travel document/pass during your journey. Anything related to such a document (validity, etc.) is your responsibility. You are legally obliged to be in the possession of a valid passport or identity card (ID) when travelling. You will find more information about insurance in the Rules section 16. 'Insurance'. 

Depending on your citizenship and your planned travel itinerary (non-Schengen area), you may need one or more visa on your passport. You will find more information about visa in the Rules section 15. 'Visa'.