You need to provide references any time that you use information from anyone else's material in your work. This applies whether you use information from a book, magazine, website, email, conversation or any other source. It also applies whether you are using exact quotations from this material , or if you put the information into your own words.
You need to reference to show your teacher that you have used high quality information, not just something that you have made up, or guessed. You also need to reference to acknowledge the work of others. Not acknowledging of the work of others, is called plagiarism. Plagiarism can get you into trouble with your teacher, teaching centre, or the law.
There are many different referencing styles in use around the world, but they all consist of two main components:
No matter which referencing style you are using , the most important thing is to clearly identify all the sources of information that you have used in your work.