A "viewer" is a person who watches something, such as a television show, movie, or online video. Viewers engage with visual content for entertainment, education, or information. They can be found in various settings, including homes, theaters, and public spaces. In the context of technology, a viewer can also refer to software or applications that display content, like images or documents. For example, a PDF viewer allows users to open and read PDF files, while a media player enables playback of audio and video files.