Citations are the way scholars acknowledge sources of the ideas in their work. Citations also tell your readers where, exactly the idea comes from in case they want to see for themselves.
Which citation style will you use?
There are many different ways to represent information about your source, which vary according to different academic disciplines. Make sure you know which style you are using, and stay consistent. Ask your professor if you aren't sure! You'll find more information on style guides at the Wichita State Libraries Citing Sources Guide.
Have citations created automatically! Be sure to check to make sure the generator is using the newest edition of your style!