With hidden survey fields, you can tag attributes to the responder's profile with out having the user select an option. This is best used when you're trying to segment your audience via attributes or further clarify the data captured in the survey.
To leverage hidden fields, follow these steps:
Go to Engage > Surveys and either create a new survey or view the questions for an existing.
Add a new survey question
Set it as a Hidden field
We will automatically map this to "Tag as attribute"
Simply enter the default value that will get tagged to the person's profile after submitting.
Save the field and you're done.
Now when someone completes this survey they will automatically be tagged with this data to their profile for segmentation.
For advanced use, you could also tie this directly to a campaign to kick-off further marketing.