A contact is a person who has been imported into Vocaza Journey at least once to complete a survey. A contact is made up of one or more respondents.
A respondent is a person who has been imported to complete a Vocaza Journey survey.
So when you access a contact's file, you can see all their requests and all their responses in a global way.
A contact is unique, whatever the survey to which it has been imported.
The uniqueness of a contact is determined by the Contact_Id field, which is mandatory for all contact imports.
Example: I import Mr John Doe so that he can respond to my survey on subscription. Mr Doe's record is created and I can see that my company has asked him to complete the subscription survey. Later, I re-import the same John Doe into Journey to answer a cancellation survey. I'll find a single John Doe contact and in his contact form, I'll see his 2 requests.