The 3GPP (3rd Generation Partnership Project, created late 90's) is aimed towards the development of standards for the various generations of mobile networks, from 3G to 5G.
The 3GPP is organized in 3 main domains or TSGs (Technical Specification Groups): Radio Access Networks (RAN), Service and Systems Aspects (SA), Core Networks and Terminals (CT). New Specifications, or new versions of a number of Specifications, are produced just after the quarterly plenary meetings for each domain.
Afterwards, the ETSI publishes the PDF versions for the releases that have been frozen (i.e. from March 2022, up to Rel‑17).
The ETSI does not publish the PDF version for studies (8xx numbers, and sometimes 7xx numbers, referred to as 'sTR' in the context of this site).
For a better overview of the contents of a specification or report, we reproduce the Table of Contents (ToC). A particularity of 3GPP standards development is that the original section numbers in a document are preserved. It can be extended, but a deleted section will appear as 'Void' and a section inserted between sections with consecutive numbers will be suffixed with a letter.
Here are some statistics in regards to 3GPP-series.