The Records value type is used for data fields which are composed of individually simple values but which, taken as a whole, are unsuitable for download via the standard mechanism - for instance being part of a multi-field structure that does not fit into a simple tabular layout.
Records type information is is distinct from blob fields in which the individual values are actually unsuitable for download.
For researchers, being approved to access a Records field also grants access to use the underlying data via both the online Data Portal or the in-situ Secure Repository.