What are the SpaceURI and ElementURI?

The SpaceURI is the unique identifier that characterizes one workspace. The SpaceURI can be found in the URL of the Explorer, for instance. It looks like the following: 
https://itonics-gmbh.itonics.io/explorer/UsHicSHE10EnYDSA

The ElementURI is the unique identifier of each content element in the system. When you open a content card in full-view mode, you'll find the element URI as the last alphanumeric code, e.g., https://itonics-gmbh.itonics.io/explorer/UsHicSHE10EnYDSA/detail/2lbeJR55bcqES4kq