A camera is a type of entity that represents a single video source in the system. The video source can either be an IP camera, or an analog camera that is connected to the video encoder of a video unit. Multiple video streams can be generated from the same video source.
A video encoder is the device that converts an analog video source to a digital format using a standard compression algorithm (H.264, MPEG- 4, or M-JPEG). The video encoder is one of the many devices found on a video unit.
Each video encoder can generate one or multiple video streams using different compression schemes and formats for different usages. In the case of an IP camera, the camera and the video encoder form an inseparable unit. Because of the relationship between the camera and the video encoder, the two terms are often used interchangeably.
Cameras (or video encoders) are automatically created when you add the video units they are part of to Security Center.