Event Stream documentation

on the documentation of the REST API there is also shortly mentioned a possibility to acces OpenHab over SSE EventStream. Unfortunatelly I have found no documentation about how a link should look like and how I can filter and access different data for example the status of a thing e.g online/offline or if an item hast changed its status, e.g on/off. So is there any documentation on it or how can I find out which possibilities are available. Thanks in advance