ELI5: Explain Like I'm 5

PMID

PMID stands for "PubMed Identifier." It is a unique number that is assigned to each medical article that is published in a scientific journal, so that it can be easily identified and found online. It tells us what book or magazine an article is from, and who wrote it. This makes it much easier to look up a particular article, especially if you only have a few details about it.