Open administrative data are those public sector data that can be re-used in the public interest, distributed and made freely available for new uses without restrictions. These are data of the administration, which are not subject to any legal restrictions (personal protection, data protection, secrecy, etc.) and open licenses, can be made available machine-readable and without costs. Ideally, these are offered in open data portals networked across various administrative levels (vertical) and subject areas (horizontal).
The video from Switzerland explains very clearly the benefits of open data using the example of the Swiss Open Government Portal.