IP camera systems have largely replaced analog CCTV. The basic architecture: IP cameras connect via Cat6 to a PoE switch or NVR with built-in PoE. The Cat6 carries both data and power (Power over Ethernet). No separate power run to each camera. Home run each camera back to the NVR or PoE switch - no daisy-chaining.
PoE power budgets matter: standard PoE (802.3af) provides 15.4W per port; PoE+ (802.3at) provides 30W; PoE++ (802.3bt) provides 60W or 90W. PTZ cameras and cameras with heaters often draw more than 15W - check the camera specs and match to the right PoE standard. The switch or NVR also has a total power budget.
Camera placement: overlap camera coverage at chokepoints (doors, driveways, parking areas), avoid shooting directly into sunlight, and think about IR illumination range at night. For exterior cameras, use outdoor-rated enclosures and weatherproof your cable penetrations. I run all exterior camera cables through conduit from the exterior camera location to an interior junction or directly to the NVR location.