Citations serve to give credit to an original author or owner of a particular work, and provide a trail back to the original source. Citations prove that you didn't make up or steal information, also known as plagiarism.
Citations also allow other scholars and professionals to check your work or learn more about a given topic. You can use Quetext's plagiarism checker to flag any instances that should be cited and generate that citation on the spot, or use the standalone Citation Generator.