CKAN uses this term to denote one of the individual data objects (a file such as a spreadsheet, or an API) in a dataset. Source: ODH

The physical representation of a dataset. Each resource can be a file of any kind, a link to a file elsewhere on the web or a link to an API. For example, if the data is being supplied in multiple formats or split into different areas or time periods, each file is a different ‘resource’ that should be described individually.

Source: http://www.w3.org/