This is Carmen. Carmen's a researcher. In this case, a scientist. Her job is to come up with ideas, and then run experiments to test the ideas. If Carmen discovers something new, she writes an article reporting her discovery.
She then sends the article off to scholarly journals, hoping they will publish it. And waits. After a few weeks or months, she finds out whether her paper is accepted, or rejected. If the publisher accepts the article, they include it in the next issue of the journal along with several other articles by other researchers. Then they publish the journal and distribute it in print and online.
Libraries - like this one - receive the journal, because they've paid for a subscription. Though nowadays it's usually an online subscription. Since the library has a subscription, it has access to many articles and issues from this journal.
The library also subscribes to hundreds or thousands of other journals. Each journal publishes several issues a year, and the library has access to many years' worth. And with several articles in each issue, this adds up to millions of articles available to the library's users. Because there are so many journals and articles, it can be hard to find the articles that are most useful to you - such as Carmen's.
Luckily, there are tools - called research databases - to help. The makers of the databases also get a copy of these journals. They split each journal back into its individual articles, and feed information about each article into a computer system - what journal it's from, the topic of the article, a summary, and more. Sometimes this even includes the full text of the articles.
Your library pays for access to these databases so that you can search them for articles related to your topic. The database's search tools allow you to quickly find articles that match your needs, such as Carmen's article. You might also uncover other articles that are useful to you! This makes it easier to find the information you need!
P.S. Just like there are many journals, there are many databases. Some will list Carmen's article and others won't. If you're not sure which database to use, or about how to find articles effectively, ask a librarian.