1. A source of information can be a book, an article, a book chapter. It can also be a webpage, an interview of someone posted on YouTube, or an encyclopedia entry. It is a piece of information that informs you about a topic. It can also be a primary source or a secondary source, depending on how it was created.
2. A source can also refer to a citation. If you need 5 sources for your paper, you must have 5 citations to different pieces of information.