In order to publish your data and make it reusable, you require a licence. A licence creates clarity and certainty for potential users of your data. A licence is not an option for all data; some of it may be too confidential or privacy-sensitive to be published.
Licences such as the Creative Commons (CC) licences replace ‘all rights reserved’ copyright with ‘some rights reserved’. There are seven standard CC licences. CC-BY is the most commonly used licence, in which attribution is mandatory when using data. You can also choose restrictions like non-commercial, no derivatives, or share alike. Creative Commons offers a guide to help you determine your preferred licence.