Trigger components tell SwisTrack when to process the next image.
Components in the Trigger category do nothing else but fire trigger events. But other components can be trigger, too. This is typically the case for input components which synchronize to the pace of acquired images. I.e. the camera notifies SwisTrack when the next image is ready to be processed.
The trigger mechanism in SwisTrack works with vetos - SwisTrack tries to execute steps as fast as possible, but but trigger components can veto that. As long as at least one component vetos, SwisTrack waits. But as soon as the last trigger component has given green light, SwisTrack immediately processes one frame.
In a setup without any trigger component, frames are processed as fast as possible. Note that this may render Swistrack to respond slowly to other inputs.