Whenever you write a paper (and this goes for your professors as well), you will have to put together a list of the sources that you used and referenced in your writing. That being said, different disciplines will have their own way of doing citations, which is why you should always ask your professor what style they want you to use. Even with all these differences, they all require the same basic information:
If you are able to identify these three things, you are well on your way to having a complete citation. All that you need is follow the rules set by the style you are using.
NOTE: Many of the databases that the library provides access to can give you the citation of the articles or books that you find during your research. Though not perfect, they are a great start and can save you a lot of time.
The links provided in this guide and by the Writing Center cover the most common citation styles. If your professor is using another style, feel free to consult with them or with the Writing Center about how to proceed and where to locate the most appropriate resources to help you complete your work.