A video encoder is the function — or the standalone device — that compresses raw video into a transmittable, storable codec stream. Inside every IP camera an encoder turns the sensor's heavy raw frames into an efficient H.264 or H.265 stream; without it, a single camera would saturate any network. As a standalone box, a "video encoder" (or video server) digitises one or more analog cameras onto an IP network, letting a modern VMS record legacy analog plant alongside IP cameras.
The encoder is where most of the bandwidth and storage decisions are actually made. Its settings — codec, resolution, frame rate, bitrate mode (constant vs variable), and GOP/keyframe interval — determine how many megabits per second a camera produces, and therefore the network and disk it will need. The same scene can cost 8 Mbps or 2 Mbps depending purely on how the encoder is configured.
The common confusion is mixing up the encoder (the device or function doing the compression) with the codec (the compression standard it applies). A pitfall on standalone encoders is treating them as a permanent solution: they keep analog cameras alive, but they inherit the analog resolution ceiling, so they are a migration bridge, not a destination.
