A publication of the U.S. National Library of Medicine (NLM). The about page for NLM gives the following overview:
The National Library of Medicine (NLM), on the campus of the National Institutes of Health in Bethesda, Maryland, has been a center of information innovation since its founding in 1836. The world’s largest biomedical library, NLM maintains and makes available a vast print collection and produces electronic information resources on a wide range of topics that are searched billions of times each year by millions of people around the globe. It also supports and conducts research, development, and training in biomedical informatics and health information technology. In addition, the Library coordinates a 6,000-member National Network of Libraries of Medicine that promotes and provides access to health information in communities across the United States.
The bulletin about page says:
The NLM Technical Bulletin, your source for the latest searching information, is produced by: MEDLARS Management Section, National Library of Medicine, Bethesda, Maryland, USA.
Which is true but seems inadequate to describe the richness of what you can find at the bulletin.
For example, in 2014 July&emdash;August No. 399 you find:
MeSH on Demand Update: How to Find Citations Related to Your Text
New Tutorial: Searching Drugs or Chemicals in PubMed
If medical terminology touches your field of interest, this is a must read.