When it comes to convincing a reader, providing evidence to support an argument/statement using another person’s/expert’s work to corroborate your assertions, is generally good practice in many forms of (written) communication. Whether it is a newspaper article or academic essay, a non-fiction book or a journal article, public policy or a tweet, on a very basic level we are more likely to be convinced by an argument if the speaker/writer shows:
So, whenever you (a writer) refer(s) to or include someone else’s words or work, whether it is a direct quote, a reproduction of a photo, or a description of an idea you (they) should always reference the source of where you (they) found that information.
In this respect, using other people’s work and effectively referencing your sources will:
The producer of a work holds the copyright to the use, and reuse, of the work itself, no matter the form: photographers retain copyright of their images; musicians of their music; and poets of their poems. Across all mediums the use of someone else’s, or even your own, work without properly crediting them constitutes plagiarism and breach of copyright.
In your academic work you can be penalised for this form of academic dishonesty, which you can read more detail about on the UCL Academic Integrity website. An understanding of how to reference effectively, using this website as a start, will help you to avoid this.