A network switch connects wired devices within a location and forwards traffic only to the port the destination device is on, which keeps the network efficient.
Unmanaged switches are plug-and-play and suit very small offices. Managed switches add VLANs, QoS, port monitoring and better security — necessary once you separate voice, CCTV and data traffic.
PoE switches deliver power over the same cable as data, which simplifies installing access points and IP cameras.
Size the switch with room to grow: count current devices, add uplink ports and allow roughly 25% spare capacity.