i. An academic source is an academic journal or book. The writer is primarily writing for an academic audience.
Examples: Journal of Popular Film & Television, International Journal of Communication, Critical Studies in Television, etc.
ii. An industry source (Trade Publications) is information from a media regulatory body or professional group. The writer is primarily writing for experts, or members of an industry, or people interested in the industry.
Examples: Advertising Age, Adweek, Billboard, Broadcasting & Cable, Hollywood Reporter, MediaWeek, Variety, etc.
iii. A popular source is a magazine or newspaper article, a blog, a website, etc. The writer is often writing for general consumption, not experts on the topic.
Examples: Entertainment Weekly, People, Rolling Stone, TV Guide, Vanity Fair, The New Yorker, etc.