The contact page is where you'll select which event attendees will receive your survey. This list is pulled directly from the Attendee list of the event you've selected.
Use the recipient list to edit attendee information (just in case something is misspelled), individually select who should get a survey, or filter out recipients by their attendance status.
Filters can be used to select those who checked-in, no-shows, or walk-ins. This allows you to better target messaging in your email (e.g. "Glad you came!" or "Sorry we missed you!") as well as your survey questions.