A static IP address is one assigned by hand and kept permanently by the device. Cameras, recorders and access controllers often use one so integrations, bookmarks and firewall rules keep working, because a changed address silently breaks every link that referenced it.
A camera that moves to a new address does not announce the change. The recorder loses its stream, the integration stops and the bookmarked page fails, usually days after the fact.
Static and reserved addresses
A static address lives in the device configuration, while a DHCP reservation keeps the address on the server and still delivers gateway and name server settings. Reservations centralize the record; statics work with no server at all.
Record what you assign
Maintain an address schedule with device, location and purpose, and exclude static addresses from the DHCP pool. Undocumented addresses produce conflicts that look like random hardware faults.