PubMed is a product of the National Center for Biotechnology Information (NCBI), at the U.S. National Library of Medicine (NLM), located at the National Institutes of Health (NIH). As a lot of life sciences research is funded by the NIH, the results of that research is required to be deposited in PubMed, making it a huge and extremely valuable open access database of material. Not every article is full-text, however; some publishers require an embargo (a period of time before an item becomes available) on their articles, so you will sometimes find bibliographical information on an article (abstract, citation) but not the full text. Stevens may have access to some of these articles, so look for the journals in the Journal Finder.
MeSH stands for Medical Subject Headings, and is the NLM-controlled vocabulary thesaurus used for indexing articles for PubMed. Thus, while you can search PubMed using keywords and find many results, you will have better luck using the specific vocabulary used by PubMed itself.