New Radio (NR) is the name given to the radio interface of the 5G specification from 3GPP which is the successor to LTE (the radio interface of the 4G specification).
Due to the history of 3GPP and the standards process the naming and organization of the specifications can be confusing. The specification documents for LTE and New Radio closest to the physical interface can be found on the 3GPP's website under "Specifications Groups">"TSG RAN">"RAN1 - Radio layer 1" > "Specifications".
Each area is broken in to a Technical Specification (TS) series with a two-part numbering scheme (separated by a .). The dictionary of first part to subject name can be found in the Specification Numbering page. You may notice that 3GPP has not learned their lesson about short-sighted naming schemes yet because the "New Radio" subject is currently under the subject of "Radio technology beyond LTE".
Each specification will have a versioning scheme that is described in the Foreword of every specification you download. The gist of it is that major version of a release number indicates when the specification is moved along the standards track and finally bumped up to the actual 3GPP Release number upon approval. From this, you can see that the first 3GPP Release with LTE (TS 36) was Release 8 on 2007-09-27 and it has gone through revision with each subsequent release.
New Radio (TS 38) was first specified in Release 15 on 2018-01-03 although it was first described in Technical Reports (TR) in Release 14. Those TRs are available from the same page as the standards but are prefixed with TR 38 (indicating a report on New Radio) rather than TS 38 (indicating a specification) on New Radio.
Moving slightly up the protocol stack, the TSG Ran Layer 2 group describes how these physical air interfaces interact with the rest of the network. TS 38.300 describes two types of gNodeB (gNB, which is the next Generation NodeB):
* gNB, which provides a New Radio user plane and control plane protocols
* nb-eNB, provides E-UTRA (the LTE air interface) user plane and control plane protocols
These are often referred to as "standalone" and "non-standalone" New Radio gNBs which enables a smooth transition to equipment that can be called 5G without breaking older equipment which was a top priority.