The NDEF spec defines a flexible way to represent different data types on an NFC chip via a set of NDEF records within an NDEF message; these record types are contextualized via a record type. The NDEF specs defines a limited set of record types, however a range of functionality can be implemented via a set of record types derived from the record types defined in the spec.
The NFC Forum defines these record types as a part of the NDEF specifications. They are the underlying, low-level NDEF record types often in which high-level, derived records types are implemented with.
These record types are not defined in the NDEF specifications as first-class concepts, but are derived from and implemented with the official NFC Forum NDEF record types. These record types are commonly used and supported by most modern NFC phones. This is a non-exhaustive list of these functional record types: