From the library's databases A-Z, you can access PubMed, PubMed Central, and Europe PMC. Each has slightly different content, and this is detailed below.
PubMed:
PubMed has been available since 1996. It contains more than 34 million references which includes the MEDLINE database plus records for articles not yet indexed with MeSH, ahead of print citations, some additional life sciences journals, author manuscripts of articles published by NIH-funded researchers, and citations for the majority of books available on the NCBI Bookshelf
PubMed Central:
PMC (PubMed Central) launched in 2000 as a free archive for full-text biomedical and life sciences journal articles. PubMed citations come from 1) MEDLINE indexed journals, 2) journals/manuscripts deposited in PMC, and 3) NCBI Bookshelf. Both MEDLINE and other PubMed citations may have links to full-text articles or manuscripts in PMC, NCBI Bookshelf, and publishers' websites. If you limit your PubMed search to MeSH controlled vocabulary or the MEDLINE subset, you will see only MEDLINE citations in your results.
Europe PMC:
Europe PMC provides access to all the abstracts in PubMed, and some other large sets of abstracts not available through PubMed (e.g. Agricola and Chinese Biological Abstracts), in addition to PMC full-text articles and other literature content of relevance to biomedical research (such as PhD theses and patents), and preprints from selected sources.