You're probably using databases all the time without knowing it. Think Amazon. Searching a library database is kind of like shopping online, except instead of looking for a new pair of shoes, you're "shopping" for journal articles, reports, news stories, etc.
An academic journal is like a magazine but instead of focusing on fashion or sports, it's all about psychology, linguistics or geography. Read the articles in them and quote them in your papers to impress your professors. (Oh, and journals are also sometimes called periodicals, just to keep things simple. ;) )
A hold is what you do when someone else has a book (or some other item) checked out of the library and you need it. Just request a hold through your library account, and we'll let you know when it arrives back at the library.
A research guide is a webpage with loads of useful links, books, e-books, search engines and databases.
A citation is all the information about a book, journal article, website etc., collected in a very specific and prescribed order and format. Writing and reading them is like riding a bike, difficult at first but once you've got the hang of it, you'll never forget.