A sign-in sheet is the paper form at reception where visitors write their name, company and arrival time. Cheap and familiar, it works for a handful of visitors a week and fails predictably beyond that: illegible entries, missed sign-outs, zero privacy (every guest reads the page), and a record locked inside the building during an evacuation.
Digital sign-in keeps the ritual and fixes the failures: legible timestamped entries, prompted sign-out, private records and a live list available anywhere. The switch usually pays for itself in front-desk time alone.