It's important to cite sources you used in your research for several reasons:
If you don't you are plagiarizing, which is a serious issue. Not only do schools take plagiarism very seriously, there could be legal repercussions...the WHS Academic Integrity Policy details the consequences if you cheat.
In order to provide evidence to support the claim in your thesis statement, you must find and borrow information or ideas from other sources; but when you do so, you have to let your audience know that is what you have done.
Any time you borrow someone else's work or ideas (words, images, video, audio) information you didn't know before you saw it, even if it's paraphrased or re-interpreted, you need to let your audience know which bits are borrowed. In other words, it MUST be cited!
Citing a source means that you show, within the body of your text and at the end of your work, that you took words, ideas, figures, images, etc. from another place.
Citations are also a way to uniquely identify a published work (e.g. book, article, chapter, web site). They are found in bibliographies and reference lists and are also collected in article and book databases.
Citations consist of standard elements, and contain all the information necessary to identify and track down publications, including:
Citations may look different, depending on what is being cited and which style was used to create them. Make sure you check with your teacher to find out what style they would like you to use.