Will call is the onsite desk or process where attendees collect badges, tickets or materials reserved in advance rather than receiving them by mail.
An attendee arrives, gives a name or an order reference, and staff find the record and hand over whatever was held for them. At most events that is now a badge printed on the spot rather than a pre-printed envelope, because printing on arrival avoids sorting thousands of badges into alphabetical trays the night before.
Mailing credentials in advance creates two problems. People forget them, and anyone who registers in the last two weeks misses the mail cut-off entirely. Holding everything at will call means one process covers every attendee regardless of when they signed up, which is also why it absorbs late changes like name corrections and ticket upgrades.
Registration is the sign-up that happened weeks ago. Will call is the collection point on the day. The distinction matters when you staff the entrance, because a will call desk that is also taking new sign-ups is running event check-in and onsite registration at the same table, and those two queues move at very different speeds.
Staff look an attendee up in the Admin App and check them in, or attendees scan a QR code at a kiosk and check themselves in while the badge prints.