You can tell that the real website to use is the first link because it has https::// in it and also gov.

You have to pay £72.50 for a new passport (adult) so they fill it in online and then they send to you what you have filled out then you sign it then you send back the documents needed to verify you are who you are. (They will send a list of the documents you need) they also need all of these documents with details on like full name, address, date of birth.