Using Boolean operators will retrieve more focused search results
AND -To obtain articles about breast cancer during pregnancy, combine the "exploded" MeSH term "PREGNANCY" with AND ""BREAST NEOPLASMS"
OR - To searcch for articles about either nosebleeds or heatstroke in children at summer camp, combine the MeSH terms: ("EPISTAXIS" OR "HEAT STROKE") AND "CAMPING" AND "CHILD"
NOT - For searching the topic of "zirconium used for knee implants," you might discover that most of the literature refers to zirconim used for oral surgery in dental work. To eliminate those citations, combine the MeSH term, "ZIRCONIUM" AND "KNEE" NOT "SURGERY, ORAL"
Simple Search
Simple search is the main search bar you'll see when you first visit PubMed. It's intended to be used like a google search - simply enter your terms as they are. No need to add AND or OR operators for this kind of simple search.
This can be a helpful place to start. You can see what might be out there and use the results to inform a more advanced search strategy if you need one!
By default, your results will be ordered by "Best Match," or relevancy, and presented in groups of ten. You can configure the display by clicking "Display Options," and selecting a different sort order (date, author, etc.), and the number of results per page.
You can also change the default "Summary" format to "Abstract," if you'd like to skim the abstracts for each reference without having to leave the results page.
Filters are available on the left hand side to further limit your results by date, study design, article type, language, and more. This can be particularly helpful for locating review articles!