Referencing is providing information on the sources that you used in your research. To ensure that your research has integrity, your sources must be credible. The original information must be easy to find to verify your statements and conclusions.
In-text Citing: short information in the body of the text.
References: Section at the end of your work with full information of works used to write the essay, to enable the reader to find the original source.
Bibliography: Strictly speaking is a list of any works read or consulted during the research, or any works recommended by the writer for further reading on the subject.
This does not require citation but what is it? It's something that you can expect your audience to know.
"The sky is blue" - no need to explain further. The fact that something is freely available on the web doesn't automatically make it "common knowledge".
Murder is wrong but if using in a legal context, you might have to quote your source.
Citation Generators can be very useful. They allow you to generate references automatically. They also provides guides for some styles: APA, Chicago, Harvard and MLA, for example. They offer a higher level of services for a subscription but the basic levels are free. Turnitin is UCC's plagiarism checker and is available through Canvas.