PubMed is a free online resource provided by the National Library of Medicine (NLM) of the United States National Institutes of Health (NIH). It is a database of biomedical literature that includes millions of citations and abstracts from scientific journals, books, and other sources. The NLM developed PubMed in the mid-1990s to provide researchers with easy access to the medical literature. PubMed is a widely used resource in the scientific community and is an important tool for researchers, clinicians, and the general public.