The FAIR principles are a set of guidelines for managing data so that they are easy to find, accessible, interoperable and reusable.
Findable : the first step in re-using data is to find them ! Data must be easy to find, both by humans and by computers. They must be in a data repository, have a persistent identifier and include metadata.
Accessible : the data and metadata are permanently available, even after the end of the project. The user knows how to access them (for example, via an identification procedure if necessary).
Interoperable : the data must be able to be used, exchanged, compared or reused in a variety of contexts. To achieve this, the data must be in a format that allows them to be combined with other data; and the user must be able to interpret them correctly.
Reusable : the reuse of data is the objective of Open Data. To achieve this, the data must be well described and documented. A clear and accessible license defines the conditions for re-use (for example, a Creative Commons licence).