Cite regardless of your format - essay, PowerPoint, website, handout, etc.
Do not cite your own research, data, ideas, opinions, observations, compositions, images, etc.
You do not have to cite common knowledge.
At times it can be difficult to know when to cite or how to properly cite a source. It may seem like more trouble than it's worth. But there are very important reasons for referencing the works of others in your research:
Giving proper credit to the original author/creator of your source is not only important from an ethical standpoint, but it also tells your audience where they can find that information for themselves.
Plagiarism has serious consequences in academia. The consequences can be even more serious outside of academia; damaged reputation, job loss, and lawsuits. There have been many famous cases of reporters, authors, politicians, and artists being caught plagiarizing.
Watch this video on a famous case of copyright breach in the music industry. It became very costly for the band The Verve. But were they the only guilty parties here?