Triggering off-camera flash
When using speedlights, there are different types of flash triggers
When using a flash, the camera and the flash device must communicate to ensure that the flash fires in sync with the shutter button. If you’re using a speedlight attached to your camera, the ‘Commander’ (CMD) mode acts as a reliable line-of-sight flash trigger, eliminating the need for an additional physical trigger. When working with offcamera flash, various triggers are available to transmit the TTL information.