In the past, nearly every project team had members who all report to the same manager and shared similar job functions. A lot of today's project teams look like that, too. But to quote Samuel L. Jackson, hold on to your butts. Because here comes "the Hollywood effect".
The name comes from the world of film production. After producers secure funding for a project, they enlist a cross-functional team of collaborators to bring it to life - think set design, makeup, wardrobe, sound, lighting, etc. Costume designers, lighting techs, and gaffers all have separate chains of command within their function (different unions, even) but they share a common purpose: to make the best movie possible. The team is formed specifically for that production and disbands when the project is complete.