A multi-device plan is a subscription that lets one account protect or use the same service on several devices, such as a laptop, phone, and tablet. In cybersecurity, this is common for VPNs, password managers, antivirus tools, and other privacy or protection services that need to follow the user across platforms.
It matters because attacks and exposures rarely stay on one device. If only a single endpoint is covered, a phone or secondary laptop may still leak data, reuse weak credentials, or connect insecurely on public Wi-Fi. A multi-device plan helps defenders apply one security control consistently across the places people actually work and browse, while also reducing the chance that an unprotected device becomes the weak link.