How does travel health insurance exactly work? As far as I've understood, I apply online for the insurance with some travel details, pay the related fee, receive the receipt in my mailbox, print several copies of it and then travel with it. But how does it work? If I feel ill for some reason in a healthcare expensive country like the US for example and I need urgent treatment, can I just enter a hospital with a copy of the receipt and be free of charges? I'd like to apply, in case, for Allianz, because they state that they directly pay all the expenses in case of need without letting the holder pay in advance and receiving a refund afterwards.
You should contact the insurer for details on how it works and what is covered and when/how/what to pay.
Normally when you go to a hospital, when filling out the various forms, you enter your insurance information.
Anecdotal: My parents were in Italy and my dad had a heart operation (needed to install a pacemaker) The hospital stay and everything medical was paid up by the travel insurances (it is between them and the hospital).
Other non-medial expenses like new plane tickets, transfer to the airport and hotel room near the airport (they had to cut short their vacation) and other things like that were paid by my parents and then reimbursed by their credit card insurances.